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SIRT7 suppresses tumorigenesis by attenuating MYC activity

ABSTRACT: SIRT7 is a member of the mammalian sirtuin family of NAD+ dependent deacylases, and interacts with RNA polymerase I and UBF to regulate rDNA transcription. Various studies in mammalian cells and human clinical data have linked SIRT7 to cancer. However studies differ as to whether SIRT7 is oncogenic or tumor suppressive. Here we analyzed SIRT7 knockout mice and found SIRT7 deficiency caused sub-Mendelian birth numbers and a reduction in body size. Moreover, at 18 month of age, roughly 60 % of the SIRT7 knockout mice develop hepatocellular carcinoma (HCC), in many cases leading to suspected metastasis. Several HCC associated genes were up-regulated in livers of mice as young as 6 months of age, particularly targets of the proto-oncogene, c- MYC. Indeed SIRT7 interacts with MYC at endogenous protein levels and also represses MYC activity. Our findings thus show that SIRT7 acts as a tumor suppressor in vivo, and may suggest novel strategies to treat liver cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE50076 | GEO | 2014/08/20

SECONDARY ACCESSION(S): PRJNA215948

REPOSITORIES: GEO

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SIRT7 suppresses tumorigenesis by attenuating MYC activity

Project description:SIRT7 is a member of the mammalian sirtuin family of NAD+ dependent deacylases, and interacts with RNA polymerase I and UBF to regulate rDNA transcription. Various studies in mammalian cells and human clinical data have linked SIRT7 to cancer. However studies differ as to whether SIRT7 is oncogenic or tumor suppressive. Here we analyzed SIRT7 knockout mice and found SIRT7 deficiency caused sub-Mendelian birth numbers and a reduction in body size. Moreover, at 18 month of age, roughly 60 % of the SIRT7 knockout mice develop hepatocellular carcinoma (HCC), in many cases leading to suspected metastasis. Several HCC associated genes were up-regulated in livers of mice as young as 6 months of age, particularly targets of the proto-oncogene, c- MYC. Indeed SIRT7 interacts with MYC at endogenous protein levels and also represses MYC activity. Our findings thus show that SIRT7 acts as a tumor suppressor in vivo, and may suggest novel strategies to treat liver cancer. The mRNAs from 3 replicates of mouse Wildtype liver compared to 3 replicates of mouse liver lacking SIRT7

2014-08-20 | E-GEOD-50076 | biostudies-arrayexpress

SIRT7 safeguards genome stability and suppresses colorectal tumorigenesis

Project description:SIRT7 is a member of the mammalian sirtuin family and functions as a NAD+-dependent deacylase. Studies in culture cells and human clinical data have implicated the role of SIRT7 in tumorigenesis. However, controversies were raised as to whether SIRT7 is oncogenic or tumor suppressive. Here we show that SIRT7 deficiency led to aneuploidy and aging-phenotypes, including senescence and nucleolin expansion. SIRT7 knockout mice were susceptible to DSS-induced colitis and alcohol-derived DNA damage, in advance led to intestinal epithelial barrier disruption. Devoid of SIRT7 aggravated the susceptibility of colorectal cancer incidence in APCMin/+ mouse model with further dysregulated Wnt signaling. Our findings indicated a tumor suppressive role of SIRT7 in vivo, novel strategies design for activating SIRT7 in treating colon cancer may be reappraised.

2020-09-16 | GSE138289 | GEO

SIRT7-dependent deacetylation of the U3-55k protein controls pre-rRNA processing [CLIP-Seq]

Project description:SIRT7 is an NAD+-dependent protein deacetylase with important roles in ribosome biogenesis and cell proliferation. Previous studies have established that SIRT7 is associated with RNA polymerase I, interacts with pre-rRNA and promotes rRNA synthesis. Here we show that SIRT7 is also associated with snoRNAs that are involved in pre-rRNA processing and rRNA maturation. Knockdown of SIRT7 impairs U3 snoRNA-dependent early cleavage steps that are necessary for generation of 18S rRNA. Mechanistically, SIRT7 deacetylates U3-55k, a core component of the U3 snoRNP complex, and reversible acetylation of U3-55k modulates the association of U3-55k with U3 snoRNA. Deacetylation by SIRT7 enhances U3-55k binding to U3 snoRNA, which is a prerequisite for pre-rRNA processing. Under stress conditions, SIRT7 is released from nucleoli, leading to hyperacetylation of U3-55k and attenuation of prerRNA processing. The results reveal a multifaceted role of SIRT7 in ribosome biogenesis, regulating both transcription and processing of rRNA. CLIP-seq was performed in Flag-SIRT7-293T cells.

2016-01-07 | E-GEOD-76578 | biostudies-arrayexpress

SIRT7 is a histone H3 lysine 18 deacetylase that regulates oncogenic transformation

Project description:Sirtuin proteins regulate diverse cellular pathways that influence genomic stability, metabolism, and ageing. SIRT7 is a mammalian sirtuin whose biochemical activity, molecular targets, and physiologic functions have been unclear. Here we show that SIRT7 is an NAD+-dependent, histone H3 acetyl-lysine 18 (H3K18Ac) deacetylase that stabilizes the transformed state of cancer cells. Genome-wide binding studies reveal that SIRT7 binds to promoters of a specific set of gene targets, where it deacetylates H3K18Ac and promotes transcriptional repression. The spectrum of SIRT7 target genes is defined in part by interaction of SIRT7 with the cancer-related ETS transcription factor ELK4, and comprises numerous genes with links to tumour suppression. Notably, selective hypoacetylation of H3K18Ac has recently been linked to oncogenic transformation, and in patients, is associated with aggressive tumour phenotypes and poor prognosis. We find that deacetylation of H3K18Ac by SIRT7 is necessary for maintaining essential features of human cancer cells including anchorage independent growth and escape from contact inhibition. Moreover, SIRT7 is necessary for a global hypoacetylation of H3K18Ac associated with cellular transformation by viral oncoproteins. Finally, SIRT7 depletion markedly reduces the tumourigenicity of human cancer cell xenografts in mice. Together, our work establishes SIRT7 as the first known site-specific H3K18Ac deacetylase and demonstrates a pivotal role for SIRT7 in chromatin regulation, cellular transformation programs, and tumour formation in vivo. SIRT7 ChIP-seq was performed in K562 cell lines under normal conditions. Two replicates were performed for both the SIRT7 ChIP as well as input control.

2012-05-06 | E-GEOD-28149 | biostudies-arrayexpress

SirT7 auto-ADPribosylation regulates glucose starvation response through macroH2A1.1 (RNA-seq)

Project description:Sirtuins are key players in the response to oxidative, metabolic and genotoxic stress, and are involved in genome stability, metabolic homeostasis and aging. Originally described as NAD+-dependent deacetylases, some sirtuins are also characterized by poorly understood mono-ADP-ribosyltransferase (MADPRT) activity. Here we report that the deacetylase SirT7 is a dual sirtuin as it also features auto-MADPRT activity. Molecular and structural evidence suggests that this novel activity occurs at a second previously undefined active site that is physically separated in another domain. Specific abrogation of this activity alters SirT7 chromatin distribution, suggesting a role for this modification in SirT7 chromatin binding specificity and localization. Our studies uncover an epigenetic pathway by which ADP-ribosyl-SirT7 is recognized by the ADP-ribose reader macroH2A1.1, a histone variant involved in chromatin organization, metabolism and differentiation. Glucose starvation (GS) boosts this interaction and promotes SirT7 re-localization intergenic regions in a macroH2A1-dependent manner, which is required for specific up- or downregulation of a subset of nearby genes upon GS in primary cells and in vivo in the livers of calorie-restricted (CR) Wt and SirT7-/- mice. The level of expression of these genes decreases with age in SirT7-deficient mice, reinforcing the link between Sirtuins, CR and aging. Our work provides a novel perspective about sirtuin duality and suggests a key role for SirT7/macroH2A1.1 axis in mammalian glucose homeostasis, calorie restriction signaling and aging.

2019-08-07 | GSE128893 | GEO

SirT7 auto-ADPribosylation regulates glucose starvation response through macroH2A1.1 (ChIP-seq)

2019-08-07 | GSE128487 | GEO

Oncogenic Potential of SIRT7 in Human Hepatocellular Carcinoma and its Regulation by the Tumor Suppressors MiR-125a-5p and MiR-125b

Project description:Sirtuins (SIRT) are NAD-dependent protein deacteylases and function in cellular metabolism, stress resistance, proliferation and disease. For SIRT7, a role in ribosomal gene transcription is proposed, but its function in cancer is currently unknown. In this study, we showed that SIRT7 expression was up-regulated in a large cohort of human hepatocellular carcinoma (HCC) patients, and that high expression of SIRT7 was associated with poor prognosis of HCC patients. Notably, inactivation of SIRT7 by siRNA suppressed tumor cell growth and caused G1/S cell cycle arrest in liver cancer cells. This treatment restored p21WAF1/Cip1 activity, induced Beclin-1 and autophagic gene expression and repressed cyclin D1. To explore mechanisms in SIRT7 regulation, microRNA (miRNA) profiling was carried out. This identified five significantly down-regulated miRNAs in HCC. Bioinformatic analysis of target sites and ectopic expression in HCC cells evidenced miR-125a-5p and miR-125b to suppress SIRT7 and cyclin D1 expression and to induce p21WAF1/Cip1-dependent G1 cell cycle arrest. Furthermore, treatment of HCC cells with 5-aza-2’-deoxycytidine or ectopic expression of wild-type but not mutated p53 restored miR-125a-5p and miR-125b expression and inhibited tumor cell growth to suggest their regulation by promoter methylation and p53 activity. To evidence clinical significance of these findings, mutations in the DNA binding domain of p53 and promoter methylation of miR-125b were investigated. Four out of nine patients with induced SIRT7 carried mutations in p53 gene and one patient showed hypermethylation of miR-125b promoter region. Conclusion: Our findings suggest that oncogenic potential of SIRT in hepatocarcinogenesis and that a regulatory loop is proposed whereby SIRT7 inhibits transcriptional activation of p21WAF1/Cip1 via repression of miR-125a-5p and miR-125b. This makes SIRT7 a promising target in cancer therapy.

2012-09-30 | GSE39678 | GEO

SIRT7 is a histone H3 lysine 18 deacetylase that regulates oncogenic transformation

2012-05-07 | GSE28149 | GEO

Identification of Oncogenic Potential of SIRT7 and Its Regulatory MicroRNAs in Liver Tumorigenesis

Project description:To investigate the specific roles of SIRT7 in the development of HCC, we employed large-scale gene expression analysis to identify the molecular signature that may affect enabling characteristics of cancer cells. Differentially expressed genes were analyzed on the Hep3B cells transfected with SIRT7 shRNAs, and recapitulated molecular signatures that related to hallmarks of cancer.

2012-03-01 | GSE33234 | GEO

SIRT7 liver

Project description:SIRT7 liver

| PRJNA896547 | ENA