Changes in gene expression have been observed in the aging human brain, but our understanding of the underlying regulatory mechanisms remains limited. To unravel these complexities, we analyzed single-nucleus gene expression, chromatin accessibility, DNA methylation, and three-dimensional (3D) chromatin architecture from human hippocampal tissues spanning the adult lifespan. We identified both linear and nonlinear dynamic gene regulatory programs during aging. Between the ages of 50 to 75, embryonic yolk sac-derived microglia were depleted and replaced by cells resembling peripheral blood monocyte-derived microglia. Hippocampal astrocytes decreased substantially with age, including those regulating synaptic transmission. Across cell types, 3D genome architecture underwent global erosion. Our analysis provides insights for how altered gene regulatory programs promote cell type-specific aging phenotypes in the human brain.

BACKGROUND:Cerebral cavernous malformations (CCM) are neurovascular lesions that affect both children and adults, and morbidity often results from thrombosis, bleeding, and neurological dysfunction. Studies indicate that inflammation-related activation of endothelial cells contributes significantly to the worsening of CCM disease. This suggests that ongoing vascular inflammation and endothelial dysfunction are key factors associated with thrombosis and bleeding in CCM disease. However, the inflammatory mechanisms leading to altered brain endothelial cell function with a high propensity for thrombosis, inflammation, and dysfunction are not fully understood. METHODS:Multi-omic analyses was conducted by performing simultaneous high-throughput single-nucleus RNA sequencing (snRNA-seq) and single-nucleus transposase-accessible chromatin sequencing (snATAC-seq) with the 10x Genomics multiome platform in combination with immunofluorescence to study CCM pathogenesis in both female and male mice with CCM (Slco1c1-CreERT2; Pdcd10 fl/fl ) disease. The analysis was complemented with bulk RNA-seq, bulk ATAC-seq, and ChIP-seq (Chromatin immunoprecipitation sequencing) using an in vitro human CCM model. An AAV-BR1 viral system selectively upregulates the activator protein-1 (AP-1) transcription factor JUNB in brain endothelial cells was used to evaluate its effectiveness in maintaining a persistent activated cell state during the pathogenesis of CCM. RESULTS:We found that epigenetics significantly influences the subtype identity and function of brain endothelial cells within the arteriovenous axis. Through multi-omic analyses, specific regulatory elements and enhancers (cis-Regulatory Elements, cCREs) in mouse brain endothelial cells were identified that influence subtype-specific transcriptional programs and the transcription factors responsible for establishing the various subtypes of brain endothelial cells. Additionally, large-scale epigenomic reprogramming of brain endothelial cell subtypes was observed during the pathogenesis of CCM disease. Among the most significant changes were alterations in the chromatin state of endothelial cells, along with transcriptional processes associated with a persistently activated endothelial cell state, which renders them susceptible to inflammation and thrombosis. The activator AP-1 transcription factor JUNB was identified as a key regulator of the persistently activated endothelial state during chronic neuroinflammation. Moreover, both trans- and cis-regulatory factors conserved between mice and humans were discovered and contribute to the progression of chronic CCM disease. CONCLUSIONS:Epigenetics plays a crucial role in determining the transcription patterns and functions of brain arteriovenous endothelial cells. The activator JUNB is identified as a driver of chronic brain vascular inflammation by inducing a persistent activated endothelial cell state from epigenome reprogramming.

The ZFX transcriptional activator binds to CpG island promoters, with a major peak at ∼200-250 bp downstream from transcription start sites. Because ZFX binds within the transcribed region, we investigated whether it regulates transcriptional elongation. We used GRO-seq to show that loss or reduction of ZFX increased Pol2 pausing at ZFX-regulated promoters. To further investigate the mechanisms by which ZFX regulates transcription, we determined regions of the protein needed for transactivation and for recruitment to the chromatin. Interestingly, although ZFX has 13 grouped zinc fingers, deletion of the first 11 fingers produces a protein that can still bind to chromatin and activate transcription. We next used TurboID-MS to detect ZFX-interacting proteins, identifying ZNF593, as well as proteins that interact with the N-terminal transactivation domain (which included histone modifying proteins), and proteins that interact with ZFX when it is bound to the chromatin (which included TAFs and other histone modifying proteins). Our studies support a model in which ZFX enhances elongation at target promoters by recruiting H4 acetylation complexes and reducing pausing.

ABSTRACT Adenovirus small e1a protein modifies host cell physiology to optimize virus replication. The N-terminal ~140 aa of e1a interacts with RB-family proteins to derepress dNTP and DNA synthesis and with EP300/CREBBP lysine acetyltransferases and EP400-TIP60 chromatin-modifying complexes to inhibit host anti-viral innate immune responses. However, the e1a N-terminal region activates a late host anti-viral response due to stabilization and activation of IRF3. The E1A C-terminal region counteracts IRF3 stabilization through interactions with three host nuclear proteins with seemingly unrelated functions. All three C-terminal interactions are required for e1a-association into a multi-protein complex with scaffold subunits of a CRL4 E3 ubiquitin ligase and DCAF10, a presumed specificity subunit. This e1a-DCAF10-CRL4 prevents IRF3 stabilization indirectly by targeting the essential AAA+ ATPases RUVBL1/2, subunits of several HSP90 co-chaperones required for quaternary assembly of cellular protein machines required for anti-viral defenses and responses to genotoxic and metabolic stress. IMPORTANCE Inactivation of EP300/CREBB paralogous cellular lysine acetyltransferases (KATs) during the early phase of infection is a consistent feature of DNA viruses. The cell responds by stabilizing transcription factor IRF3 which activates transcription of scores of interferon-stimulated genes (ISGs), inhibiting viral replication. Human respiratory adenoviruses counter this by assembling a CUL4-based ubiquitin ligase complex that polyubiquitinylates RUVBL1 and 2 inducing their proteasomal degradation. This inhibits accumulation of active IRF3 and the expression of anti-viral ISGs, allowing replication of the respiratory HAdVs in the face of inhibition of EP300/CBEBBP KAT activity by the N-terminal region of E1A.

Regulation of RNA polymerase II (Pol2) elongation in the promoter-proximal region is an important and ubiquitous control point for gene expression in metazoans. We report that transcription of the adenovirus 5 E4 region is regulated during the release of paused Pol2 into productive elongation by recruitment of the super-elongation complex, dependent on promoter H3K18/27 acetylation by CBP/p300. We also establish that this is a general transcriptional regulatory mechanism that applies to ~7% of expressed protein-coding genes in primary human airway epithelial cells. We observed that a homeostatic mechanism maintains promoter, but not enhancer, H3K18/27ac in response to extensive inhibition of CBP/p300 acetyl transferase activity by the highly specific small molecule inhibitor A-485. Further, our results suggest a function for BRD4 association at enhancers in regulating paused Pol2 release at nearby promoters. Taken together, our results uncover the processes regulating transcriptional elongation by promoter region histone H3 acetylation and homeostatic maintenance of promoter, but not enhancer, H3K18/27ac in response to inhibition of CBP/p300 acetyl transferase activity.

Adenovirus E1A early proteins modify host cell physiology to optimize virus replication. The N-terminal half of small e1a interacts with RB-family proteins to de-repress dNTP and DNA synthesis, and with p300/CBP to inhibit host anti-viral innate immune responses. These e1a N-terminal interactions activate a strong, late host anti-viral response due to stabilization and activation of interferon response factor 3 (IRF3). However, the C-terminal half of e1a inhibits this through interactions with three host proteins with seemingly unrelated functions. Proteomic analysis showed that all three C-terminal interactions are required for e1a-association into an ∼1 MDa multi-protein complex with scaffold subunits of a CRL4 E3 ubiquitin ligase and DCAF10, a presumed specificity subunit. This e1a-DCAF10-CRL4 prevents IRF3 stabilization indirectly by directing degradation of the essential AAA+ ATPases RUVBL1/2, subunits of several HSP90 co-chaperones required for quaternary assembly of cellular protein machines required for anti-viral defenses and responses to genotoxic and metabolic stress.### Competing Interest StatementThe authors have declared no competing interest.

How histone acetylation promotes transcription is not clearly understood. Here, we confirm an interaction between p300 and the adenovirus 2 large E1A activation domain (AD) and map the interacting regions in E1A by observing colocalization at an integrated lacO array of fusions of LacI-mCherry to E1A fragments with YFP-p300. Viruses with mutations in E1A subdomains were constructed and analyzed for kinetics of early viral RNA expression and association of acetylated H3K9, K18, K27, TBP, and RNA polymerase II (Pol II) across the viral genome. The results indicate that this E1A interaction with p300 is required for H3K18 and H3K27 acetylation at the E2early, E3, and E4 promoters and is required for TBP and Pol II association with the E2early promoter. In contrast, H3K18/27 acetylation was not required for TBP and Pol II association with the E3 and E4 promoters but was required for E4 transcription at a step subsequent to Pol II preinitiation complex assembly.IMPORTANCE Despite a wealth of data associating promoter and enhancer region histone N-terminal tail lysine acetylation with transcriptional activity, there are relatively few examples of studies that establish causation between these histone posttranslational modifications and transcription. While hypoacetylation of histone H3 lysines 18 and 27 is associated with repression, the step(s) in the overall process of transcription that is blocked at a hypoacetylated promoter is not clearly established in most instances. Studies presented here confirm that the adenovirus 2 large E1A protein activation domain interacts with p300, as reported previously (P. Pelka, J. N. G. Ablack, J. Torchia, A. S. Turnell, R. J. A. Grand, J. S. Mymryk, Nucleic Acids Res 37:1095-1106, 2009, https://doi.org/10.1093/nar/gkn1057), and that the resulting acetylation of H3K18/27 affects varied steps in transcription at different viral promoters.

Colorectal cancer remains the third most common cause of death from cancer worldwide. MicroRNA emerges as a good area of research for current cancer therapy. Here, we identified miR-135b to be a contributor to anti-apoptosis and chemoresistance in colorectal cancer. We observed high levels of miR-135b in colorectal cancer cell lines and clinical tissues, compared to colorectal epithelium cell line and noncancerous tissues. Furthermore, enforced expression of miR-135b attenuated doxorubicin-induced apoptosis in colorectal cells. (Doxorubicin alone can trigger significant apoptosis). In elucidating the molecular mechanism by which miR-135b participate in the regulation of apoptosis and chemoresistance in colorectal cancer, we discovered that large tumor suppressor kinase 2 (LATS2) is a direct target of miR-135b. The role of miR-135b was confirmed in colorectal tumor xenograft models. The growth of established tumors was suppressed by an inhibition of miR-135b expression and enhanced apoptosis was further assessed by TUNEL assay. Taken together, our results reveal that miR-135b and LATS2 axis may be a novel therapeutic target for colorectal cancer.

Upstream ORFs are elements found in the 5'-leader sequences of specific mRNAs that modulate the translation of downstream ORFs encoding major gene products. In Arabidopsis, the translational control of auxin response factors (ARFs) by upstream ORFs has been proposed as a regulatory mechanism required to respond properly to complex auxin-signaling inputs. In this study, we identify and characterize the aberrant auxin responses in specific ribosomal protein mutants in which multiple ARF transcription factors are simultaneously repressed at the translational level. This characteristic lends itself to the use of these mutants as genetic tools to bypass the genetic redundancy among members of the ARF family in Arabidopsis. Using this approach, we were able to assign unique functions for ARF2, ARF3, and ARF6 in plant development.