Introduction Radiation sialadenitis is a debilitating complication of head and neck cancer radiotherapy for which no effective therapy exists. Conventional MSC-based strategies face translational barriers, and crude MSC-conditioned medium (MSC-CM) provides only limited efficacy, underscoring the need for cell-free alternatives. Materials and methods Rat salivary gland MSCs were characterized and cultured on porcine decellularized matrix hydrogel to generate optimized concentrated conditioned medium (CC-CM). CC-CM was tested in irradiated SGMSCs and in a rat submandibular gland irradiation model; senescence, apoptosis, and transcriptomic changes were assessed. Apoptosis dependence was examined using the pan-caspase inhibitor Z-VAD-FMK, and senescent cell clearance was evaluated by flow cytometry, live-cell imaging, and co-staining for senescence and apoptosis markers. Results and discussion CC-CM demonstrated markedly superior therapeutic effects against radiation sialadenitis compared with conventional MSC-CM. Mechanistically, irradiation induces an early apoptosis-resistant state in SGMSCs that precedes the senescence phenotype, and the accumulated senescent cells are refractory to apoptosis. CC-CM eliminates these pathogenic senescent cells, exhibiting senolytic activity. Dynamic live cell imaging revealed that CC-CM restores the impaired apoptotic process in irradiated SGMSCs. CC-CM increased the number of dead cells in a caspase-dependent manner, and co-staining for senescence markers and cleaved caspase-3 confirmed that CC-CM directs senescent cells into apoptosis. This senolytic activity was further validated in vivo in irradiated submandibular gland tissues. Pharmacological blockade of apoptosis attenuated the therapeutic effects of CC-CM, establishing the functional necessity of apoptosis restoration. Conclusion Tissue-specific decellularized matrix priming endows the MSC secretome with the capacity to eliminate radiation-induced senescent cells through restoration of the apoptotic program. This mechanism-based, cell-free platform represents a promising strategy for treating radiation-induced salivary gland injury.

Disordered osteogenic potential in bone marrow mesenchymal stem cells (BMSCs) is a hallmark of inflammatory jaw diseases. Recent studies suggest that inflammatory stimulating disrupts energy metabolism during BMSC osteogenesis. However, the impact of key metabolites on BMSC ossification remains unclear. In this study, a comprehensive targeted metabolomics analysis was performed during BMSC osteogenic differentiation, with and without inflammatory stimulation induced by lipopolysaccharide (LPS). We identified a significant downregulation of spermidine (SPD), along with methylated purines and pyrimidines, in the inflammatory environment. Exogenous SPD supplementation enhanced BMSC osteogenesis and increased N6-methyladenosine (m6A) methylation. Mechanistically, SPD elevated S-adenosylmethionine (SAM) levels and upregulated the methyltransferases METTL3 and METTL14. Similarly, betaine, a promoter of SAM synthesis, increased m6A methylation and improved BMSC osteogenic potential. In contrast, the METTL3/METTL14 inhibitor S-adenosylhomocysteine (SAH) reduced m6A methylation and negated SPD's osteogenic effects. This suggests that SPD enhances BMSC osteogenesis through m6A methylation regulation. Furthermore, SPD activated autophagy in BMSCs, while SAH inhibited SPD-induced autophagy. Notably, treatment with rapamycin (Rap), an autophagy inducer, restored both autophagy and osteogenic differentiation impaired by SAH. In vivo, SPD supplementation enhanced m6A methylation and facilitated bone regeneration in a rat model of inflammatory mandibular defects. In conclusion, this study demonstrates that SPD promotes the osteogenic potential of BMSCs through an m6A methylation-autophagy axis under inflammatory conditions, providing a novel therapeutic approach for inflammatory jaw diseases.

Oral cancers are characterized by aggressive loco-regional invasion and high recurrence rates, leading to poor patient outcomes. Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin, has demonstrated potent antitumor activity. However, its underlying effects and mechanisms on oral cancer cell migration have not been fully elucidated. This study found that DHA significantly inhibited cell motility by disrupting cytoskeletal organization, cell membrane fluidity, and mitochondrial function. Moreover, DHA inhibited tumor cell migration (P < 0.01) through a dual mechanism involving cytoskeletal disruption and reduced membrane fluidity, which may contribute to suppressing pseudopodia formation and cell polarity maintenance. Herein our data suggested that the effects of DHA treatment could be related to mTORC1-inhibited RhoA/Rac1/Cdc42 signaling (leading to cytoskeletal destabilization, P < 0.05) and mTORC1-inhibited SREBP1 protein expression (altering lipid metabolism and decreasing membrane fluidity, P < 0.05). We speculated that the combined impact of the multiple pathways leads to the disruption of cell polarity, ultimately impairing tumor cell migration. Additionally, DHA altered mitochondrial bioenergetics, to reduce ATP production essential for tumor migration. Notably, a selective mitophagy inhibitor Mdivi-1 can further enhance the anti-migratory effects of DHA, suggesting a potential strategy for the combination treatment. Taken together, our findings highlighted the capacity of DHA to inhibit oral cancer cell migration through a multifaceted mechanism involving cytoskeletal regulation, lipid metabolism, and mitochondrial dysfunction. The study supported that DHA-based treatment may be a novel option for anti-metastatic therapies in oral cancer.

Cadmium (Cd) is a widespread environmental heavy metal pollutant known to disrupt bone metabolism, causing significant health concerns. Cd exposure impairs osteogenesis in primary bone marrow-derived mesenchymal stem cells (BMSCs) through mechanisms involving oxidative stress and NF-kappa B inflammation signaling. However, the underlying effects and mechanisms by which Cd hampers bone defect repair remain largely unknown. Additionally, alpha-ketoglutarate (AKG) is a dietary supplement as an antioxidant to potentially improve healthy longevity. In this study, we used a rat model to investigate the toxicology mechanisms of Cd to suppress bone repair and identify orally administrated AKG as a potential therapeutic intervention. Herein, we demonstrated that Cd inhibited BMSC and vascular endothelial cell motility, markedly reducing lamellipodia formation and cell migration. Cd also disrupted cytoskeletal reorganization and cell adhesion in BMSCs. Moreover, our data indicated that Cd induced abnormal expression of RhoA protein and suppressed the Notch1 pathway. In vivo studies further revealed that Cd significantly impaired cranial bone defect repair, tissue healing, and the formation of new vascular structures. These findings suggested that Cd interfered with BMSC migration and homing to bone defect sites, obstructing bone repair and healing. Intriguingly, AKG partially restored Cd-impaired BMSC mobilization and exhibited partial efficacy in ameliorating cranial bone defect repair compromised by Cd. Our study uncovered a novel mechanism by which Cd exposure impeded bone repair and presented AKG administration as a potential approach to mitigate Cd-induced bone tissue damage. This work may broaden our current understanding of Cd-induced bone disorders.

The increasing prevalence of type 2 diabetes mellitus (T2DM) worldwide presents significant challenges in the management of impaired tissue repair in diabetic skin wounds, which has emerged as a critical health concern. Addressing this issue while minimizing adverse effects remains crucial. Allulose has been shown to exhibit hypolipidemic and anti-inflammatory properties, alleviating obesity and atherosclerosis by improving insulin resistance and impaired glucose tolerance. However, its underlying effects and mechanisms in repairing diabetic skin damage remain poorly understood. In this study, we demonstrated that oral administration of allulose remarkably ameliorated T2DM-compromised skin tissue wound associated with the stimulation of skin granulation, surrounding tissue formation, and activated fibroblasts, under high-fat diet (HFD) feeding condition. In addition, administration partially promoted collagen deposition, reduced M1 macrophage polarization, facilitated neovascularization, and mitigated tissue inflammation in the T2DM rats upon HFD feeding. Moreover, allulose could significantly alleviate high glucose stress condition-induced inflammatory response, correlative with modulation of p38/NLRP3/Caspase-1 signaling. In addition, allulose could also ameliorate high glucose stress-compromised cell viability and proliferative capacity, related to stimulation of mTOR pathway in part. Taken together, our study revealed that T2DM compromised some certain factors which are crucial for skin tissue healing and wound repair upon HFD condition. The work highlighted the potential beneficial effects of orally administered allulose for healing diabetic skin wounds and supported a novel strategy for managing diabetes patients adjunctively with allulose dietary supplement.

Stress-induced premature senescent (SIPS) cells induced by various stresses deteriorate cell functions. Dasatinib and quercetin senolytics (DQ) can alleviate several diseases by eliminating senescent cells. α-tricalcium phosphate (α-TCP) is a widely used therapeutic approach for bone restoration but induces bone formation for a comparatively long time. Furthermore, bone infection exacerbates the detrimental prognosis of bone formation during material implant surgery due to oral cavity bacteria and unintentional contamination. It is essential to mitigate the inhibitory effects on bone formation during surgical procedures. Little is known that DQ improves bone formation in Lipopolysaccharide (LPS)-contaminated implants and its intrinsic mechanisms in the study of maxillofacial bone defects. This study aims to investigate whether the administration of DQ ameliorates the impairments on bone repair inflammation and contamination by eliminating SIPS cells. α-TCP and LPS-contaminated α-TCP were implanted into Sprague-Dawley rat calvaria bone defects. Simultaneously, bone formation in the bone defects was investigated with or without the oral administration of DQ. Micro-computed tomography and hematoxylin-eosin staining showed that senolytics significantly enhanced bone formation at the defect site. Histology and immunofluorescence staining revealed that the levels of p21- and p16-positive senescent cells, inflammation, macrophages, reactive oxygen species, and tartrate-resistant acid phosphatase-positive cells declined after administering DQ. DQ could partially alleviate the production of senescent markers and senescence-associated secretory phenotypes in vitro. This study indicates that LPS-contaminated α-TCP-based biomaterials can induce cellular senescence and hamper bone regeneration. Senolytics have significant therapeutic potential in reducing the adverse osteogenic effects of biomaterial-related infections and improving bone formation capacity.

Cadmium (Cd) is a widespread environmental and industrial pollutant to cause various bone metabolic diseases. Our former study reported that Cd promoted adipogenesis and inhibited osteogenic differentiation of primary bone marrow-derived mesenchymal stem cells (BMSCs) by NF-κB inflammation signaling and oxidative stress, and Cd-induced osteoporosis of long bone and compromised repair of cranial bone defect in vivo. However, the underlying mechanisms of Cd-induced bone damage remain elusive. In this study, we used Sprague Dawley (SD) rat and NLRP3-knockout mouse models to elucidate the exact effects and molecular mechanisms of Cd-induced bone damage and aging. Herein we found that the exposure of Cd preferentially targeted a few specific tissues such as bone and kidney. Cd triggered NLRP3 inflammasome pathways and the accumulation of autophagosomes of primary BMSCs, and also Cd stimulated the differentiation and bone resorption function of primary osteoclasts. Moreover, Cd not only activated ROS/NLRP3/caspase-1/p20/IL-1β pathways, but also influenced Keap1/Nrf2/ARE signaling. The data revealed that autophagy dysfunction and NLRP3 pathways synergistically mediated the impairments of Cd in bone tissues. Loss of NLRP3 function partially alleviated Cd-induced osteoporosis and craniofacial bone defect in the NLRP3-knockout mouse model. Furthermore, we characterized the protective effects and potential therapeutic targets of the combined treatment of anti-aging agents (rapamycin+melatonin+NLRP3 selective inhibitor MCC950) on Cd-induced bone damage and inflammatory aging. These results illuminate that ROS/NLRP3 pathways and autophagic flux obstruction are involved in the Cd-induced toxic actions of bone tissues. Collectively, our study unveils some therapeutic targets and the regulatory mechanism to prevent Cd-caused bone rarefaction. The findings improve the mechanistic understanding of environmental Cd exposure-caused bone metabolism disorders and tissue damage.

Oral squamous cell carcinoma (OSCC), with aggressive locoregional invasion, has a high rate of early recurrences and poor prognosis. Dihydroartemisinin (DHA), as a derivative of artemisinin, has been found to exert potent antitumor activity. Recent studies reported that DHA suppresses OSCC cell growth and viability through the regulation of reactive oxygen species (ROS) production and mitochondrial calcium uniporter. However, the mechanism underlying the action of DHA on OSCCs remains elusive. In the study, we observed that 159 genes were remarkably misregulated in primary OSCC tumors associated with DHA-inhibited pathways, supporting that OSCCs are susceptible to DHA treatment. Herein, our study showed that DHA exhibited promising effects to suppress OSCC cell growth and survival, and single-cell colony formation. Interestingly, the combination of DHA and cisplatin (CDDP) significantly reduced the toxicity of CDDP treatment alone on human normal oral cells (NOK). Moreover, DHA remarkably impaired mitochondrial structure and function, and triggered DNA damage and ROS generation, and activation of mitophagy. In addition, DHA induced leakage of cytochrome C and apoptosis-inducing factor (AIF) from mitochondria, elevated Bax/cleaved-caspase 3 expression levels and compromised Bcl2 protein expression. In the OSCC tumor-xenograft mice model, DHA remarkably suppressed tumor growth and induced apoptosis of OSCCs in vivo. Intriguingly, a selective mitophagy inhibitor Mdivi-1 could significantly reinforce the anticancer activity of DHA treatment. DHA and Mdivi-1 can synergistically suppress OSCC cell proliferation and survival. These data uncover a previously unappreciated contribution of the mitochondria-associated pathway to the antitumor activity of DHA on OSCCs. Our study shed light on a new aspect of a DHA-based therapeutic strategy to combat OSCC tumors.

Cadmium (Cd) is a heavy metal toxicant as a common pollutant derived from many agricultural and industrial sources. The absorption of Cd takes place primarily through Cd-contaminated food and water and, to a significant extent, via inhalation of Cd-contaminated air and cigarette smoking. Epidemiological data suggest that occupational or environmental exposure to Cd increases the health risk for osteoporosis and spontaneous fracture such as itai-itai disease. However, the direct effects and underlying mechanism(s) of Cd exposure on bone damage are largely unknown. We used primary bone marrow-derived mesenchymal stromal cells (BMMSCs) and found that Cd significantly induced BMMSC cellular senescence through over-activation of NF-κB signaling pathway. Increased cell senescence was determined by production of senescence-associated secretory phenotype (SASP), cell cycle arrest and upregulation of p21/p53/p16INK4a protein expression. Additionally, Cd impaired osteogenic differentiation and increased adipogenesis of BMMSCs, and significantly induced cellular senescence-associated defects such as mitochondrial dysfunction and DNA damage. Sprague-Dawley (SD) rats were chronically exposed to Cd to verify that Cd significantly increased adipocyte number, and decreased mineralization tissues of bone marrow in vivo. Interestingly, we observed that Cd exposure remarkably retarded bone repair and regeneration after operation of skull defect. Notably, pretreatment of melatonin is able to partially prevent Cd-induced some senescence-associated defects of BMMSCs including mitochondrial dysfunction and DNA damage. Although Cd activated mammalian target of rapamycin (mTOR) pathway, rapamycin only partially ameliorated Cd-induced cell apoptosis rather than cellular senescence phenotypes of BMMSCs. In addition, a selective NF-κB inhibitor moderately alleviated Cd-caused the senescence-related defects of the BMMSCs. The study shed light on the action and mechanism of Cd on osteoporosis and bone ageing, and may provide a novel option to ameliorate the harmful effects of Cd exposure.

Cohesin loader nipped‐B‐like protein (Nipbl) is increasingly recognized for its important role in development and cancer. Cornelia de Lange Syndrome (CdLS), mostly caused by heterozygous mutations of Nipbl, is an autosomal dominant disease characterized by multiorgan malformations. However, the regulatory role and underlying mechanism of Nipbl in skeletal development remain largely elusive. In this study, we constructed a Nipbl‐a Cas9‐knockout (KO) zebrafish, which displayed severe retardation of global growth and skeletal development. Deficiency of Nipbl remarkably compromised cell growth and survival, and osteogenic differentiation of mammalian osteoblast precursors. Furthermore, Nipbl depletion impaired the cell cycle process, and caused DNA damage accumulation and cellular senescence. In addition, nucleolar fibrillarin expression, global rRNA biogenesis, and protein translation were defective in the Nipbl‐depleted osteoblast precursors. Interestingly, an integrated stress response inhibitor (ISRIB), partially rescued Nipbl depletion‐induced cellular defects in proliferation and apoptosis, osteogenesis, and nucleolar function. Simultaneously, we performed transcriptome analysis of Nipbl deficiency on human neural crest cells and mouse embryonic fibroblasts in combination with Nipbl ChIP‐Seq. We found that Nipbl deficiency caused thousands of differentially expressed genes including some important genes in bone and cartilage development. In conclusion, Nipbl deficiency compromised skeleton development through impairing osteoblast precursor cell proliferation and survival, and osteogenic differentiation, and also disturbing the expression of some osteogenesis‐regulatory genes. Our study elucidated that Nipbl played a pivotal role in skeleton development, and supported the fact that treatment of ISRIB may provide an early intervention strategy to alleviate the bone dysplasia of CdLS.

Oral squamous cell carcinoma (OSCC) is the major cause of morbidity and mortality in head and neck cancer patients worldwide. This malignant disease is challenging to treat because of the lack of effective curative strategies and the high incidence of recurrence. This study aimed to investigate the efficacy of a single and dual approach targeting ribosome biogenesis and protein translation to treat OSCC associated with the copy number variation (CNV) of ribosomal DNA (rDNA). Here, we found that primary OSCC tumors frequently exhibited a partial loss of 45S rDNA copy number and demonstrated a high susceptibility to CX5461 (a selective inhibitor of RNA polymerase I) and the coadministration of CX5461 and INK128 (a potent inhibitor of mTORC1/2). Combined treatment displayed the promising synergistic effects that induced cell apoptosis and reactive oxygen species (ROS) generation, and inhibited cell growth and proliferation. Moreover, INK128 compromised NHEJ-DNA repair pathway to reinforce the antitumor activity of CX5461. In vivo, the cotreatment synergistically suppressed tumor growth, triggered apoptosis and strikingly extended the survival time of tumor-bearing mice. Additionally, treatment with the individual compounds and coadministration appeared to reduce the incidence of enlarged inguinal lymph nodes. Our study supports that the combination of CX5461 and INK128 is a novel and efficacious therapeutic strategy that can combat this cancer and that 45S rDNA may serve as a useful indicator to predict the efficacy of this cotreatment.

头颈部鳞状细胞癌（HNSCC）在全球最常见的恶性肿瘤中位居第六,晚期患者转移并复发率高,预后较差,为患者家庭和社会经济带来严重损失。靶向药物结合经典放化疗的个性化方案有望提高治疗功效并延长生存期。磷脂酰肌醇3-激酶/蛋白激酶B/哺乳动物雷帕霉素靶蛋白（PI3K/Akt/m TOR）在HNSCC中普遍存在过度激活,是控制肿瘤发生、发展及研发靶向药物的重要通路本文就PI3K/Akt/m TOR通路应用于HNSCC靶向治疗的个体性差异发生的潜在机制,以及临床试验取得的进展与目前所面临的困境进行探讨,拟为HNSCC的临床靶向治疗提供参考思路,从而提高患者的生存质量。

Abstract Ribosomal DNA is one of the most variable regions in the human genome with respect to copy number, yet we know virtually nothing about what governs its copy number, stability, and sequence. Ribosomal DNA is present in many tandem repeats that are incredibly important because 1) they encode the template for the RNA component of ribosomes, 2) they organize large parts of nearly every human chromosome and 3) they can titrate factors involved in chromosomal processes, with profound impact on DNA replication, repair, and gene expression. We applied computational and droplet digital PCR approaches to explore rDNA copy number in normal and cancer states in human and mouse genomes. We find that the copy number is similar between tissues from the same mouse, and is similar within inbred mouse strains, but can vary widely between individuals in an outbred strain. PTEN is a tumor suppressor and negative regulator of mTOR activity that is critical for genome stability. We find that hematopoietic stem cells from a PTEN-/- mouse model for leukemia have lower rDNA copy number than normal tissue, associated with hypersensitivity to DNA damage. Remarkably, analysis of three human cancer genome projects reveals low rDNA copy number relative to matched normal tissue. Our analysis reveals a genomic signature associated with hyperactive mTOR in osteosarcoma that includes loss of rDNA copies accompanied by an increase in sequence heterogeneity, as well as additional genes that co-vary in copy number. PTEN-mTOR may normally contribute to maintenance of ribosomal DNA. This abstract is also being presented as Poster A38. Citation Format: Baoshan Xu, Hua Li, John Perry, Bethany Harris, Brian Slaughter, Jay Unruh, Vijay Pratap Singh, Musinu Zakari, William McDowell, Linheng Li, Jennifer L. Gerton. PTEN-mTOR pathway serves as a guardian of ribosomal DNA. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr PR06.

NIPBL, a cohesin loader, has been implicated in transcriptional control and genome organization. Mutations in NIPBL, cohesin, and its deacetylase HDAC8 result in Cornelia de Lange syndrome. We report activation of the RNA-sensing kinase PKR in human lymphoblastoid cell lines carrying NIPBL or HDAC8 mutations, but not SMC1A or SMC3 mutations. PKR activation can be triggered by unmodified RNAs. Gene expression profiles in NIPBL-deficient lymphoblastoid cells and mouse embryonic stem cells reveal lower expression of genes involved in RNA processing and modification. NIPBL mutant lymphoblastoid cells show reduced proliferation and protein synthesis with increased apoptosis, all of which are partially reversed by a PKR inhibitor. Non-coding RNAs from an NIPBL mutant line had less m(6) A modification and activated PKR activity in vitro. This study provides insight into the molecular pathology of Cornelia de Lange syndrome by establishing a relationship between NIPBL and HDAC8 mutations and PKR activation.

All living organisms must go through cycles of replicating their genetic information and then dividing the copies between two new cells. This cyclical process, in cells from bacteria and human alike, requires a protein complex known as cohesin. Cohesin is a structural maintenance of chromosomes (SMC) complex. While bacteria have one form of this complex, yeast have several SMC complexes, and humans have at least a dozen cohesin complexes alone. Therefore the ancient structure and function of SMC complexes has been both conserved and specialized over the course of evolution. These complexes play roles in replication, repair, organization, and segregation of the genome. Mutations in the genes that encode cohesin and its regulatory factors are associated with developmental disorders such as Roberts syndrome, Cornelia de Lange syndrome, and cancer. In this review, we focus on how acetylation of cohesin contributes to its function. In Roberts syndrome, the lack of cohesin acetylation contributes to nucleolar defects and translational inhibition. An understanding of basic SMC complex function will be essential to unraveling the molecular etiology of human diseases associated with defective SMC function.

All living organisms must go through cycles of replicating their genetic information and then dividing the copies between two new cells. This cyclical process, in cells from bacteria and human alike, requires a protein complex known as cohesin. Cohesin is a structural maintenance of chromosomes (SMC) complex. While bacteria have one form of this complex, yeast have several SMC complexes, and humans have at least a dozen cohesin complexes alone. Therefore the ancient structure and function of SMC complexes has been both conserved and specialized over the course of evolution. These complexes play roles in replication, repair, organization, and segregation of the genome. Mutations in the genes that encode cohesin and its regulatory factors are associated with developmental disorders such as Roberts syndrome, Cornelia de Lange syndrome, and cancer. In this review, we focus on how acetylation of cohesin contributes to its function. In Roberts syndrome, the lack of cohesin acetylation contributes to nucleolar defects and translational inhibition. An understanding of basic SMC complex function will be essential to unraveling the molecular etiology of human diseases associated with defective SMC function.

Roberts syndrome (RBS) is a human disease characterized by defects in limb and craniofacial development and growth and mental retardation. RBS is caused by mutations in ESCO2, a gene which encodes an acetyltransferase for the cohesin complex. While the essential role of the cohesin complex in chromosome segregation has been well characterized, it plays additional roles in DNA damage repair, chromosome condensation, and gene expression. The developmental phenotypes of Roberts syndrome and other cohesinopathies suggest that gene expression is impaired during embryogenesis. It was previously reported that ribosomal RNA production and protein translation were impaired in immortalized RBS cells. It was speculated that cohesin binding at the rDNA was important for nucleolar form and function. We have explored the hypothesis that reduced ribosome function contributes to RBS in zebrafish models and human cells. Two key pathways that sense cellular stress are the p53 and mTOR pathways. We report that mTOR signaling is inhibited in human RBS cells based on the reduced phosphorylation of the downstream effectors S6K1, S6 and 4EBP1, and this correlates with p53 activation. Nucleoli, the sites of ribosome production, are highly fragmented in RBS cells. We tested the effect of inhibiting p53 or stimulating mTOR in RBS cells. The rescue provided by mTOR activation was more significant, with activation rescuing both cell division and cell death. To study this cohesinopathy in a whole animal model we used ESCO2-mutant and morphant zebrafish embryos, which have developmental defects mimicking RBS. Consistent with RBS patient cells, the ESCO2 mutant embryos show p53 activation and inhibition of the TOR pathway. Stimulation of the TOR pathway with L-leucine rescued many developmental defects of ESCO2-mutant embryos. Our data support the idea that RBS can be attributed in part to defects in ribosome biogenesis, and stimulation of the TOR pathway has therapeutic potential.

Cohesin is a protein complex known for its essential role in chromosome segregation. However, cohesin and associated factors have additional functions in transcription, DNA damage repair, and chromosome condensation. The human cohesinopathy diseases are thought to stem not from defects in chromosome segregation but from gene expression. The role of cohesin in gene expression is not well understood. We used budding yeast strains bearing mutations analogous to the human cohesinopathy disease alleles under control of their native promoter to study gene expression. These mutations do not significantly affect chromosome segregation. Transcriptional profiling reveals that many targets of the transcriptional activator Gcn4 are induced in the eco1-W216G mutant background. The upregulation of Gcn4 was observed in many cohesin mutants, and this observation suggested protein translation was reduced. We demonstrate that the cohesinopathy mutations eco1-W216G and smc1-Q843Δ are associated with defects in ribosome biogenesis and a reduction in the actively translating fraction of ribosomes, eiF2α-phosphorylation, and (35)S-methionine incorporation, all of which indicate a deficit in protein translation. Metabolic labeling shows that the eco1-W216G and smc1-Q843Δ mutants produce less ribosomal RNA, which is expected to constrain ribosome biogenesis. Further analysis shows that the production of rRNA from an individual repeat is reduced while copy number remains unchanged. Similar defects in rRNA production and protein translation are observed in a human Roberts syndrome cell line. In addition, cohesion is defective specifically at the rDNA locus in the eco1-W216G mutant, as has been previously reported for Roberts syndrome. Collectively, our data suggest that cohesin proteins normally facilitate production of ribosomal RNA and protein translation, and this is one way they can influence gene expression. Reduced translational capacity could contribute to the human cohesinopathies.

The Prestwick and NIH chemical libraries were screened for drugs that protect baker’s yeast from sugar-induced cell death (SICD). SICD is triggered when stationary-phase yeast cells are transferred from spent rich medium into water with 2% glucose and no other nutrients. The rapid, apoptotic cell death occurs because reactive oxygen species (ROS) accumulate. We found that triclabendazole, which is used to treat liver flukes in cattle and man, partially protects against SICD. Characterization of triclabendazole revealed that it also protects yeast cells from death induced by the Parkinson’s disease-related protein alpha-synuclein (α-syn), which is known to induce the accumulation of ROS.