Mitochondria are hubs of metabolism and signaling. We previously demonstrated the importance of mitochondrial structure and function in chemotherapy-refractory triple-negative breast cancer (TNBC). Herein, we present the first 3D analysis of mitochondrial networks in human tumor tissues. Using serial block face scanning electron microscopy, we reconstructed 3,750 mitochondria and 800 lipid droplets (LDs) in naive and residual tumors persisting after conventional chemotherapies in two orthotopic patient-derived xenografts (PDX). Chemotherapies administered as monotherapy or in combination produced residual tumors that harbored mitochondria with significantly increased areas, volumes, and perimeters. We observed substantial reduction of mitochondrial intratumor heterogeneity following all treatments. Further, mitochondrial complexity was significantly elevated after single-agent treatments in one model, but was reduced in the other PDX model. Mitochondria-LD significantly increased contacts in residual tumors, congruent with our previous studies providing evidence for rewiring of lipid metabolism in residual TNBC. These results highlight the potential for structure-based monitoring of chemotherapy-induced metabolic rewiring in TNBC.

ABSTRACT Nuclear entry of HIV-1 involves specific interactions between the viral capsid and components of the nuclear pore complex. FG-repeat sequences present in many nucleoporins play important roles in HIV-1 nuclear entry. We previously reported that overexpression of the FG repeat-containing C-terminal fragment of the nucleoporin POM121C (residues 614–987), termed POM987, inhibits HIV-1 infection. However, the mechanism underlying this inhibition remained unclear. Here, we identified HIV-1 escape mutants that are resistant to POM987-mediated restriction and mapped the responsible mutations to two amino acid positions in the capsid protein. POM987 bound the incoming HIV-1 capsid core and inhibited viral nuclear entry. In contrast, the escape mutant showed reduced interaction with POM987 and restored nuclear entry and integration in POM987-expressing cells. These findings indicate that the antiviral activity of POM987 is mediated by capsid-dependent inhibition of HIV-1 nuclear entry and suggest that capsid–nucleoporin interactions could provide a potential target for developing novel antiviral therapies.IMPORTANCEHIV-1 can infect non-dividing cells. This requires interaction with nuclear pore proteins, including POM121C. A mis-localized fragment of POM121C potently inhibits nuclear entry through direct interaction with the incoming capsid core. Escape variants acquire mutations at specific capsid residues, enabling them to evade this interaction and thereby restore nuclear import.

Although Sorting and Assembly Machinery 50 (SAM50) is known to regulate nutritional and metabolic stress related to ageing, its exact role is not well understood. This experimental study combines both human and animal models to understand the role that SAM50 plays in nutrient, age-related metabolic remodeling. We also wanted to define the clinical relevance of SAMM50 genetic variation in human disease. Our study integrated clinical and genetic data from three large and independent human biobanks to assess the clinical implications of genetic variation in SAMM50. We then conducted mechanistic studies in mice using Serial Block-Face Scanning Electron Microscopy and Transmission Electron Microscopy for three-dimension analysis of mitochondrial morphology, immunoblotting, metabolomics/lipidomics, and assessment of metabolic parameters in models of fasting, aging, and a high-fat diet (HFD). Descriptive and inferential statistics were used to describe and test associations in GraphPad prism version 10. Our study demonstrated that common genetic variation within the SAMM50 genetic locus was significantly associated with liver-related metabolic disorders. In mice, nutrient status was associated with expression levels of Sam50 and proteins involved in the respiratory complex. Aging was associated with impaired mitochondria, decreased Sam50 expression, and increased triglyceride and lipid peroxidation, with increased lipid droplet-mitochondria contacts. An HFD was associated with a reduction in Sam50 expression, disruption of mitochondrial structure, and metabolic dysfunction, effects that were only partly reversed by returning to a normal diet. Our results demonstrate that SAM50 expression is associated with nutrient state and age-related signals, thereby orchestrating mitochondrial structure to influence systemic metabolic health.

Due to aging, the efficiency of kidney function begins to decrease. Dysfunction in mitochondria and their cristae is a hallmark of aging. Therefore, age-related decline in kidney function could be attributed to changes in mitochondrial ultrastructure, increased reactive oxygen species, and alterations in metabolism and lipid composition. We sought to understand how mitochondrial ultrastructure is altered over time in tubular kidney cells. A serial block face-scanning electron microscope and manual segmentation using the Amira software were employed to visualize murine kidney samples during the aging process at 3 months (young) and 2 years (old). We found that 2-year mitochondria are more fragmented with many uniquely shaped mitochondria observed across aging, concomitant with shifts in ROS, metabolomics, and lipid homeostasis. Furthermore, we demonstrate that the mitochondrial contact site and cristae organizing system (MICOS) complex is impaired in the kidney during aging. Disruption of the MICOS complex resulted in altered mitochondrial metabolic function and increased ROS levels. We found significant, detrimental structural changes in the mitochondria of aged kidney tubules, suggesting a potential mechanism underlying the increased frequency of kidney disease with aging. We hypothesize that disruption of the MICOS complex exacerbates mitochondrial dysfunction, creating a vicious cycle of mitochondrial degradation and oxidative stress, which impacts kidney health.

Alzheimer's Disease (AD) is a global health issue, affecting over 6 million people in the United States, with that number expected to increase as the population ages. As a neurodegenerative disorder that affects memory and cognitive functions, it is well established that AD is associated with cardiovascular risk factors beyond only cerebral decline. In this study, we measured hemodynamic parameters related to cardiovascular and cerebrovascular function in 5xFAD mice with AD and their littermates. Specifically, we measured cardiovascular pulse wave velocity parameters, a marker of arterial stiffness and cardiovascular risk, and cerebrovascular pulse wave velocity, a novel technique to measure cerebral arterial stiffness. Our results showed that while 5xFAD mice exhibited significant differences in ejection time, pulse pressure, and Tei index, many other cardiovascular and cerebral parameters were not different. Despite reports that amyloid plaque deposition begins at an early age of 1.5 months in 5xFAD mice, our results did not indicate significant cardiovascular changes. Studies to elucidate cardiovascular and cerebrovascular parametric changes should be done at later ages where the underlying changes are more profound.

Mitochondrial contact site and cristae organizing system (MICOS) complexes are critical for maintaining the mitochondrial architecture, cristae integrity, and organelle communication in neurons. MICOS disruption has been implicated in neurodegenerative disorders, including Alzheimer's disease (AD), yet the spatiotemporal dynamics of MICOS-associated neuronal alterations during aging remain unclear. Using three-dimensional reconstructions of hypothalamic and cortical neurons, we observed age-dependent fragmentation of mitochondrial cristae, reduced intermitochondrial connectivity, and compartment-specific changes in mitochondrial size and morphology. Notably, these structural deficits were most pronounced in neurons vulnerable to AD-related pathology, suggesting a mechanistic link between MICOS disruption and the early mitochondrial dysfunction observed in patients with AD. Our findings indicate that the loss of MICOS integrity is a progressive feature of neuronal aging, contributing to impaired bioenergetics and reduced resilience to metabolic stress and potentially facilitating neurodegenerative processes. MICOS disruption reduced neuronal firing and synaptic responsiveness, with miclxin treatment decreasing mitochondrial connectivity and inducing cristae disorganization. These changes link MICOS structural deficits directly to impaired neuronal excitability, highlighting vulnerability to AD-related neurodegeneration. These results underscore the importance of MICOS as a critical determinant of neuronal mitochondrial health and as a potential target for interventions aimed at mitigating AD-related mitochondrial dysfunction.

Retroviral replication has two distinctive features, reverse transcription of the viral ssRNA genome into a dsDNA and integration of the viral DNA into the host genome. Viral DNA integration establishes a provirus in the host genome that resides as a stable viral genetic element for the life of the cell and serves as the source of progeny virion production. However, integration requires the viral preintegration complex (PIC) to overcome the structural barriers of the densely packed chromatin to access the host DNA. Eukaryotic chromosomes are organized by the repeating units of nucleosomes. A nucleosome comprises of a DNA segment of ∼150 base pairs compacted by an octamer of histone proteins, which regulate access to the DNA through a network of chemical modifications. Interestingly, several histone tail modifications play an outsized role in regulating retroviral integration into specific regions of the host genome. Studies in the last few decades have identified several viral and host factors that promote retroviral integration and regulate integration targeting. However, the interaction between the PIC and host nucleosomes that promote retroviral integration is an understudied area. In this review, we will focus on the biochemical and molecular interactions of retroviral PICs with the host nucleosome in an attempt to identify the barriers and factors involved in retroviral integration.

Cleavage and polyadenylation specificity factor 6 (CPSF6) is part of the cellular cleavage factor I mammalian (CFIm) complex that regulates mRNA processing and polyadenylation. CPSF6 also functions as an HIV-1 capsid (CA) binding host factor to promote viral DNA integration targeting into gene-dense regions of the host genome. However, the effects of CPSF6 on the activity of the HIV-1 preintegration complex (PIC)-the sub-viral machinery that carries out viral DNA integration-are unknown. To study CPSF6's role in HIV-1 PIC function, we extracted PICs from cells that are either depleted of CPSF6 or express a mutant form that cannot bind to CA. These PICs exhibited significantly lower viral DNA integration activity when compared to the control PICs. The addition of purified recombinant CPSF6 restored the integration activity of PICs extracted from the CPSF6-mutant cells, suggesting a direct role of CPSF6 in PIC function. To solidify CPSF6's role in PIC function, we inoculated CPSF6-depleted and CPSF6-mutant cells with HIV-1 particles and measured viral DNA integration into the host genome. A significant reduction in integration in these cells was detected, and this reduction was not a consequence of lower reverse transcription or nuclear entry. Additionally, mutant viruses deficient in CA-CPSF6 binding showed no integration defect in CPSF6-mutant cells. Finally, sequencing analysis revealed that HIV-1 integration into CPSF6-mutant cell genomes was significantly redirected away from gene-dense regions of chromatin compared to the control cells. Collectively, these results suggest that the CPSF6-CA interaction promotes PIC function both in vitro and in infected cells.IMPORTANCEHIV-1 infection is dependent on the interaction of the virus with cellular host factors. However, the molecular details of HIV-host factor interactions are not fully understood. For instance, the HIV-1 capsid provides binding interfaces for several host factors. CPSF6 is one such capsid-binding host factor, whose cellular function is to regulate mRNA processing and polyadenylation. Initial work identified a truncated cytosolic form of CPSF6 to restrict HIV infection by blocking viral nuclear entry. However, it is now established that the full-length CPSF6 primarily promotes HIV-1 integration targeting into gene-dense regions of the host genome. Here, we provide evidence that CPSF6-CA interaction stimulates the activity of HIV-1 preintegration complexes (PICs). We also describe that disruption of CPSF6-CA binding in target cells significantly reduces viral DNA integration and redirects integration targeting away from gene-dense regions into regions of low transcriptional activity. These findings identify a critical role for the CPSF6-CA interaction in PIC function and integration targeting.

Cyclophilin A (CypA) binds to the HIV-1 capsid to facilitate reverse transcription and nuclear entry and counter the antiviral activity of TRIM5 alpha. Interestingly, recent studies suggest that the capsid enters the nucleus of an infected cell and uncoats prior to integration. We have previously reported that the capsid protein regulates HIV-1 integration. Therefore, we probed whether CypA-capsid interaction also regulates this post-nuclear entry step. First, we challenged CypA-expressing (CypA(+/+)) and CypA-depleted (CypA(-/-)) cells with HIV-1 and quantified the levels of provirus. CypA-depletion significantly reduced integration, an effect that was independent of CypA's effect on reverse transcription, nuclear entry, and the presence or absence of TRIM5 alpha. In addition, cyclosporin A, an inhibitor that disrupts CypA-capsid binding, inhibited proviral integration in CypA(+/+) cells but not in CypA(-/-) cells. HIV-1 capsid mutants (G89V and P90A) deficient in CypA binding were also blocked at the integration step in CypA(+/+) cells but not in CypA(-/-) cells. Then, to understand the mechanism, we assessed the integration activity of the HIV-1 preintegration complexes (PICs) extracted from acutely infected cells. PICs from CypA(-/-) cells retained lower integration activity in vitro compared to those from CypA(+/+) cells. PICs from cells depleted of both CypA and TRIM5 alpha also had lower activity, suggesting that CypA's effect on PIC was independent of TRIM5 alpha. Finally, CypA protein specifically stimulated PIC activity, as this effect was significantly blocked by CsA. Collectively, these results provide strong evidence that CypA directly promotes HIV-1 integration, a previously unknown role of this host factor in the nucleus of an infected cell.

The liver, the largest internal organ and a metabolic hub, undergoes significant declines due to aging, affecting mitochondrial function and increasing the risk of systemic liver diseases. How the mitochondrial three-dimensional (3D) structure changes in the liver across aging, and the biological mechanisms regulating such changes confers remain unclear. In this study, we employed Serial Block Face-Scanning Electron Microscopy (SBF-SEM) to achieve high-resolution 3D reconstructions of murine liver mitochondria to observe diverse phenotypes and structural alterations that occur with age, marked by a reduction in size and complexity. We also show concomitant metabolomic and lipidomic changes in aged samples. Aged human samples reflected altered disease risk. To find potential regulators of this change, we examined the Mitochondrial Contact Site and Cristae Organizing System (MICOS) complex, which plays a crucial role in maintaining mitochondrial architecture. We observe that the MICOS complex is lost during aging, but not Sam50. Sam50 is a component of the sorting and assembly machinery (SAM) complex that acts in tandem with the MICOS complex to modulate cristae morphology. In murine models subjected to a high-fat diet, there is a marked depletion of the mitochondrial protein SAM50. This reduction in Sam50 expression may heighten the susceptibility to liver disease, as our human biobank studies corroborate that Sam50 plays a genetically regulated role in the predisposition to multiple liver diseases. We further show that changes in mitochondrial calcium dysregulation and oxidative stress accompany the disruption of the MICOS complex. Together, we establish that a decrease in mitochondrial complexity and dysregulated metabolism occur with murine liver aging. While these changes are partially be regulated by age-related loss of the MICOS complex, the confluence of a murine high-fat diet can also cause loss of Sam50, which contributes to liver diseases. In summary, our study reveals potential regulators that affect age-related changes in mitochondrial structure and metabolism, which can be targeted in future therapeutic techniques.

HIV-1 integration into the human genome is dependent on 3’-processing of the viral DNA. Recently, we reported that the cellular Three Prime Repair Exonuclease 1 (TREX1) enhances HIV-1 integration by degrading the unprocessed viral DNA, while the integration-competent 3’-processed DNA remained resistant. Here, we describe the mechanism by which the 3’-processed HIV-1 DNA resists TREX1-mediated degradation. Our kinetic studies revealed that the rate of cleavage (kcat) of the 3’-processed DNA was significantly lower (approximately 2-2.5-fold) than the unprocessed HIV-1 DNA by TREX1. The kcat values of human TREX1 for the processed U5 and U3 DNA substrates were 3.8 s-1 and 4.5 s-1, respectively. In contrast, the unprocessed U5 and U3 substrates were cleaved at 10.2 s-1 and 9.8 s-1, respectively. The efficiency of degradation (kcat/Km) of the 3’-processed DNA (U5-70.2 and U3-28.05 pM-1s-1) was also significantly lower than the unprocessed DNA (U5-103.1 and U3-65.3 pM-1s-1). Furthermore, the binding affinity (Kd) of TREX1 was markedly lower (∼ 2-fold) for the 3’-processed DNA compared to the unprocessed DNA. Molecular docking and dynamics studies revealed distinct conformational binding modes of TREX1 with the 3’-processed and unprocessed HIV-1 DNA. Particularly, the unprocessed DNA was favorably positioned in the active site with polar interactions with the catalytic residues of TREX1. Additionally, a stable complex was formed between TREX1 and the unprocessed DNA compared the 3’-processed DNA. These results pinpoint the mechanism by which TREX1 preferentially degrades the integration-incompetent HIV-1 DNA and reveal the unique structural and conformational properties of the integration-competent 3’-processed HIV-1 DNA.

Prolidase (PEPD) is the only hydrolase that cleaves the dipeptides containing C-terminal proline or hydroxyproline- the rate-limiting step in collagen biosynthesis. However, the molecular regulation of prolidase expression remains largely unknown. In this study, we have identified overlapping binding sites for the transcription factors- Krüppel‐like factor 6 (KLF6) and Specificity protein 1 (Sp1) in the PEPD promoter and demonstrate that KLF6/Sp1 transcriptionally regulate prolidase expression. By cloning the PEPD promoter into a luciferase reporter and through site-directed deletion, we pinpointed the minimal sequences required for KLF6 and Sp1-mediated PEPD promoter-driven transcription. Interestingly, Sp1 inhibition abrogated KLF6-mediated PEPD promoter activity, suggesting that Sp1 is required for the basal expression of prolidase. We further studied the regulation of PEPD by KLF6 and Sp1 during transforming growth factor β1 (TGF-β1) signaling, since both KLF6 and Sp1 are key players in TGF-β1 mediated collagen biosynthesis. Mouse and human fibroblasts exposed to TGF-β1 resulted in the induction of PEPD transcription and prolidase expression. Inhibition of TGF-β1 signaling abrogated PEPD promoter-driven transcriptional activity of KLF6 and Sp1. Knock-down of KLF6 as well as Sp1 inhibition also reduced prolidase expression. Chromatin immunoprecipitation assay supported direct binding of KLF6 and Sp1 to the PEPD promoter and this binding was enriched by TGF-β1 treatment. Finally, immunofluorescence studies showed that KLF6 co-operates with Sp1 in the nucleus to activate prolidase expression and enhance collagen biosynthesis. Collectively, our results identify functional elements of the PEPD promoter for KLF6 and Sp1-mediated transcriptional activation and describe the molecular mechanism of prolidase expression.

Chronic inflammation contributes to the prevalence of cardiovascular disease in people living with HIV (PLWH). The immune mechanisms driving atherosclerosis progression in PLWH remain unclear. This study conducted comprehensive assessments of medium-sized coronary arteries and aorta from deceased PLWH and controls without HIV using DNA/RNA assays, spatial transcriptomics, and high-resolution mass spectrometry. Findings revealed more significant inflammation correlated with higher HIV copy numbers in late atheroma of PLWH. Enhanced CXCL12 and decreased ABCA1/ABCG1 expression in CD163+ macrophages were co-localized in coronaries of PLWH, suggesting a reduction in plasma lipoprotein clearance compared to controls. Spatial analyses identified potential therapeutic targets by revealing inflammatory changes in medium-sized arteries and the aorta. We examined the relationship between atherosclerotic phenotypes and inflammatory gene expression in Vanderbilts Biobank to study these findings in a larger clinical cohort. This established a significant association between ABCA1 and CXCL12 gene expressions with atherosclerosis, partly influenced by HIV.

HIV type 1 (HIV-1) is the causative agent of AIDS. Since the start of the epidemic, HIV/AIDS has been responsible for ≈40 million deaths. Additionally, an estimated 39 million people are currently infected with the virus. HIV-1 primarily infects immune cells, such as CD 4+ (cluster of differentiation 4 + ) T lymphocytes (T cells), and as a consequence, the number of CD 4+ T cells progressively declines in people living with HIV. Within a span of ≈10 years, HIV-1 infection leads to the systemic failure of the immune system and progression to AIDS. Fortunately, potent antiviral therapy effectively controls HIV-1 infection and prevents AIDS-related deaths. The efficacy of the current antiviral therapy regimens has transformed the outcome of HIV/AIDS from a death sentence to a chronic disease with a prolonged lifespan of people living with HIV. However, antiviral therapy is not curative, is challenged by virus resistance, can be toxic, and, most importantly, requires lifelong adherence. Furthermore, the improved lifespan has resulted in an increased incidence of non-AIDS–related morbidities in people living with HIV including cardiovascular diseases, renal disease, liver disease, bone disease, cancer, and neurological conditions. In this review, we summarize the current state of knowledge of the cardiovascular comorbidities associated with HIV-1 infection, with a particular focus on hypertension. We also discuss the potential mechanisms known to drive HIV-1–associated hypertension and the knowledge gaps in our understanding of this comorbid condition. Finally, we suggest several directions of future research to better understand the factors, pathways, and mechanisms underlying HIV-1–associated hypertension in the post-antiviral therapy era.

ABSTRACTThe human immunodeficiency virus type 1 (HIV-1) genome encodes 15 proteins that perform structural, enzymatic, regulatory, and accessory functions. The capsid protein (CA) is the primary structural protein of HIV-1 and plays multiple functions during infection. Early studies predicted that HIV-1 CA mainly protected and delivered the viral genome to the target cell. However, it is now well established that CA plays a critical role after the cellular entry steps of infection. During the early stages, CA promotes reverse transcription of the RNA genome into a DNA copy and the nuclear import/entry step of HIV-1 infection. Emerging evidence also supports the functional role of CA in the post-nuclear entry steps of infection, such as HIV-1 integration. During the late stages of infection, CA coordinates hexameric lattice formation for the assembly of immature virion. CA also regulates theformation of the mature capsid that encases the viral genome and associated factors in the infectious progeny virion. Because of these indispensable roles, HIV-1 CA has emerged as a new and validated target for antiviral drug development. Accordingly, the first CA-targeting drug, lenacapavir (GS-6207), was recently approved to treat certain HIV-1-infected individuals whose viral load cannot be controlled by other antiviral drugs. Still, new and superior CA inhibitors are needed to qualify as part of the front-line antiviral therapy regimens for all infected individuals. The development of such inhibitors requires a clear understanding of CA’s role in HIV-1 infection. In this review, we will describe CA’s role during the early stages of HIV-1 infection, with particular emphasis on post-nuclear entry steps.IMPORTANCEHIV-1 capsid protein (CA)—independently or by recruiting host factors—mediates several key steps of virus replication in the cytoplasm and nucleus of the target cell. Research in the recent years have established that CA is multifunctional and genetically fragile of all the HIV-1 proteins. Accordingly, CA has emerged as a validated and high priority therapeutic target, and the first CA-targeting antiviral drug was recently approved for treating multi-drug resistant HIV-1 infection. However, development of next generation CA inhibitors depends on a better understanding of CA’s known roles, as well as probing of CA’s novel roles, in HIV-1 replication. In this timely review, we present an updated overview of the current state of our understanding of CA’s multifunctional role in HIV-1 replication—with a special emphasis on CA’s newfound post-nuclear roles, highlight the pressing knowledge gaps, and discuss directions for future research.

BACKGROUND:There is an urgent need to increase diversity among scientific investigators in the HIV research field to be more reflective of communities highly affected by the HIV epidemic. Thus, it is critical to promote the inclusion and advancement of early-stage scholars from racial and ethnic groups underrepresented in HIV science and medicine.METHODS:To widen the HIV research career pathway for early-stage scholars from underrepresented minority groups, the National Institutes of Health supported the development of the Centers for AIDS Research (CFAR) Diversity, Equity, and Inclusion Pathway Initiative (CDEIPI). This program was created through partnerships between CFARs and Historically Black Colleges and Universities and other Minority Serving Institutions throughout the United States.RESULTS:Seventeen CFARs and more than 20 Historically Black Colleges and Universities and Minority Serving Institutions have participated in this initiative to date. Programs were designed for the high school (8), undergraduate (13), post baccalaureate (2), graduate (12), and postdoctoral (4) levels. Various pedagogical approaches were used including didactic seminar series, intensive multiday workshops, summer residential programs, and mentored research internship opportunities. During the first 18 months of the initiative, 257 student scholars participated in CDEIPI programs including 150 high school, 73 undergraduate, 3 post baccalaureate, 27 graduate, and 4 postdoctoral students.CONCLUSION:Numerous student scholars from a wide range of educational levels, geographic backgrounds, and racial and ethnic minority groups have engaged in CDEIPI programs. Timely and comprehensive program evaluation data will be critical to support a long-term commitment to this unique training initiative.

The HIV-1 genome encodes a small number of proteins with structural, enzymatic, regulatory, and accessory functions. These viral proteins interact with a number of host factors to promote the early and late stages of HIV-1 infection. During the early stages of infection, interactions between the viral proteins and host factors enable HIV-1 to enter the target cell, traverse the cytosol, dock at the nuclear pore, gain access to the nucleus, and integrate into the host genome. Similarly, the viral proteins recruit another set of host factors during the late stages of infection to orchestrate HIV-1 transcription, translation, assembly, and release of progeny virions. Among the host factors implicated in HIV-1 infection, Cyclophilin A (CypA) was identified as the first host factor to be packaged within HIV-1 particles. It is now well established that CypA promotes HIV-1 infection by directly binding to the viral capsid. Mechanistic models to pinpoint CypA's role have spanned from an effect in the producer cell to the early steps of infection in the target cell. In this review, we will describe our understanding of the role(s) of CypA in HIV-1 infection, highlight the current knowledge gaps, and discuss the potential role of this host factor in the post-nuclear entry steps of HIV-1 infection.

Background: The Southern region of the United States has the highest HIV incidence, and new infections disproportionately affect Black Americans. The Tennessee Center for AIDS Research (CFAR) Diversity, Equity, and Inclusion Pathway Initiative (CDEIPI) program supports the training of individuals from groups underrepresented in medicine and science in multiple areas of research to increase the pool of HIV-focused investigators at early educational and career stages. Setting: The Tennessee CFAR is a partnership between Vanderbilt University Medical Center, Meharry Medical College (one of the oldest historically Black medical colleges), Tennessee Department of Health, and Nashville Community AIDS Resources, Education and Services (a sophisticated community service organization, which emphasizes research training responsive to regional and national priorities). Methods: The Tennessee CFAR CDEIPI program leverages existing Vanderbilt University Medical Center and Meharry Medical College structured biomedical training programs for high school and undergraduate students to provide an intensive, mentored, HIV research experience augmented by CFAR resources situating this training within the broader history, scientific breadth, and societal and political aspects of the HIV epidemic. Results: The first year of the Tennessee CFAR CDEIPI program trained 3 high school and 3 undergraduate students from underrepresented in medicine and science backgrounds in basic, clinical/translational, and community-focused research projects with a diverse group of 9 mentors. All students completed the program, and evaluations yielded positive feedback regarding mentoring quality and effectiveness, and continued interest in HIV-related research. Conclusions: The Tennessee CFAR CDEIPI program will continue to build upon experience from the first year to further contribute to national efforts to increase diversity in HIV-related research.

HIV-1 DNA is preferentially integrated into chromosomal hot spots by the preintegration complex (PIC). To understand the mechanism, we measured the DNA integration activity of PICs-extracted from infected cells-and intasomes, biochemically assembled PIC substructures using a number of relevant target substrates. We observed that PIC-mediated integration into human chromatin is preferred compared to genomic DNA. Surprisingly, nucleosomes lacking histone modifications were not preferred integration compared to the analogous naked DNA. Nucleosomes containing the trimethylated histone 3 lysine 36 (H3K36me3), an epigenetic mark linked to active transcription, significantly stimulated integration, but the levels remained lower than the naked DNA. Notably, H3K36me3-modified nucleosomes with linker DNA optimally supported integration mediated by the PIC but not by the intasome. Interestingly, optimal intasome-mediated integration required the cellular cofactor LEDGF. Unexpectedly, LEDGF minimally affected PIC-mediated integration into naked DNA but blocked integration into nucleosomes. The block for the PIC-mediated integration was significantly relieved by H3K36me3 modification. Mapping the integration sites in the preferred substrates revealed that specific features of the nucleosome-bound DNA are preferred for integration, whereas integration into naked DNA was random. Finally, biochemical and genetic studies demonstrate that DNA condensation by the H1 protein dramatically reduces integration, providing further evidence that features inherent to the open chromatin are preferred for HIV-1 integration. Collectively, these results identify the optimal target substrate for HIV-1 integration, report a mechanistic link between H3K36me3 and integration preference, and importantly, reveal distinct mechanisms utilized by the PIC for integration compared to the intasomes. IMPORTANCE HIV-1 infection is dependent on integration of the viral DNA into the host chromosomes. The preintegration complex (PIC) containing the viral DNA, the virally encoded integrase (IN) enzyme, and other viral/host factors carries out HIV-1 integration. HIV-1 integration is not dependent on the target DNA sequence, and yet the viral DNA is selectively inserted into specific "hot spots" of human chromosomes. A growing body of literature indicates that structural features of the human chromatin are important for integration targeting. However, the mechanisms that guide the PIC and enable insertion of the PIC-associated viral DNA into specific hot spots of the human chromosomes are not fully understood. In this study, we describe a biochemical mechanism for the preference of the HIV-1 DNA integration into open chromatin. Furthermore, our study defines a direct role for the histone epigenetic mark H3K36me3 in HIV-1 integration preference and identify an optimal substrate for HIV-1 PIC-mediated viral DNA integration.