Maf1 regulates intracellular lipid homeostasis in response to DNA damage response activation.
Ontology highlight
ABSTRACT:
SUBMITTER: Hammerquist AM
PROVIDER: S-EPMC8351542 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:ObjectiveRECQL4 (a member of the RECQ helicase family) upregulation has been reported to be associated with tumor progression in several malignancies. However, whether RECQL4 sustains esophageal squamous cell carcinoma (ESCC) has not been elucidated. In this study, we determined the functional role for RECQL4 in ESCC progression.MethodsRECQL4 expression in clinical samples of ESCC was examined by immunohistochemistry. Cell proliferation, cellular senescence, the epithelial-mesenchymal transition (EMT), DNA damage, and reactive oxygen species in ESCC cell lines with RECQL4 depletion or overexpression were analyzed. The levels of proteins involved in the DNA damage response (DDR), cell cycle progression, survival, and the EMT were determined by Western blot analyses.ResultsRECQL4 was highly expressed in tumor tissues when compared to adjacent non-tumor tissues in ESCC (P < 0.001) and positively correlated with poor differentiation (P = 0.011), enhanced invasion (P = 0.033), and metastasis (P = 0.048). RECQL4 was positively associated with proliferation and migration in ESCC cells. Depletion of RECQL4 also inhibited growth of tumor xenografts in vivo. RECQL4 depletion induced G0/G1 phase arrest and cellular senescence. Importantly, the levels of DNA damage and reactive oxygen species were increased when RECQL4 was depleted. DDR, as measured by the activation of ATM, ATR, CHK1, and CHK2, was impaired. RECQL4 was also shown to promote the activation of AKT, ERK, and NF-kB in ESCC cells.ConclusionsThe results indicated that RECQL4 was highly expressed in ESCC and played critical roles in the regulation of DDR, redox homeostasis, and cell survival.
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Project description:The E3 ubiquitin ligase RNF8 (RING finger protein 8) is a pivotal enzyme for DNA repair. However, RNF8 hyper-accumulation is tumour-promoting and positively correlated with genome instability, cancer cell invasion, metastasis, and poor patient prognosis. Very little is known about the mechanisms regulating RNF8 homeostasis to preserve genome stability. We identify the cellular machinery, composed of the p97/VCP ubiquitin-dependent unfoldase/segregase and the Ataxin 3 (ATX3) deubiquitinase, which together form a physical and functional complex with RNF8 to regulate its proteasome-dependent homeostasis under physiological conditions. Under genotoxic stress, when RNF8 is rapidly recruited to sites of DNA lesions, the p97-ATX3 machinery stimulates the extraction of RNF8 from chromatin to balance DNA repair pathway choice and promote cell survival after ionising radiation (IR). Inactivation of the p97-ATX3 complex affects the non-homologous end joining DNA repair pathway and hypersensitises human cancer cells to IR. We propose that the p97-ATX3 complex is the essential machinery for regulation of RNF8 homeostasis under both physiological and genotoxic conditions, and that targeting ATX3 may be a promising strategy to radio-sensitise BRCA-deficient cancers.
| S-SCDT-EMBOJ-2019-102361 | biostudies-other
Project description:The E3 ubiquitin ligase RNF8 (RING finger protein 8) is a pivotal enzyme for DNA repair. However, RNF8 hyper-accumulation is tumour-promoting and positively correlates with genome instability, cancer cell invasion, metastasis and poor patient prognosis. Very little is known about the mechanisms regulating RNF8 homeostasis to preserve genome stability. Here, we identify the cellular machinery, composed of the p97/VCP ubiquitin-dependent unfoldase/segregase and the Ataxin 3 (ATX3) deubiquitinase, which together form a physical and functional complex with RNF8 to regulate its proteasome-dependent homeostasis under physiological conditions. Under genotoxic stress, when RNF8 is rapidly recruited to sites of DNA lesions, the p97-ATX3 machinery stimulates the extraction of RNF8 from chromatin to balance DNA repair pathway choice and promote cell survival after ionising radiation (IR). Inactivation of the p97-ATX3 complex affects the non-homologous end joining DNA repair pathway and hypersensitises human cancer cells to IR. We propose that the p97-ATX3 complex is the essential machinery for regulation of RNF8 homeostasis under both physiological and genotoxic conditions and that targeting ATX3 may be a promising strategy to radio-sensitise BRCA-deficient cancers.
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Project description:MutL homolog 1 (MLH1) is a key DNA mismatch repair protein, which plays an important role in maintenance of genomic stability and the DNA damage response. Here, we report that MLH1 is a novel substrate of histone deacetylase 6 (HDAC6). HDAC6 interacts with and deacetylates MLH1 both in vitro and in vivo Interestingly, deacetylation of MLH1 blocks the assembly of the MutSα-MutLα complex. Moreover, we have identified four novel acetylation sites in MLH1 by MS analysis. The deacetylation mimetic mutant, but not the WT and the acetylation mimetic mutant, of MLH1 confers resistance to 6-thioguanine. Overall, our findings suggest that the MutSα-MutLα complex serves as a sensor for DNA damage response and that HDAC6 disrupts the MutSα-MutLα complex by deacetylation of MLH1, leading to the tolerance of DNA damage.
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Project description:The cellular response to genotoxic stress is mediated by a well-characterized network of DNA surveillance pathways. The contribution of post-transcriptional gene regulatory networks to the DNA damage response (DDR) has not been extensively studied. Here, we systematically identified RNA-binding proteins differentially interacting with polyadenylated transcripts upon exposure of human breast carcinoma cells to ionizing radiation (IR). Interestingly, more than 260 proteins, including many nucleolar proteins, showed increased binding to poly(A)+ RNA in IR-exposed cells. The functional analysis of DDX54, a candidate genotoxic stress responsive RNA helicase, revealed that this protein is an immediate-to-early DDR regulator required for the splicing efficacy of its target IR-induced pre-mRNAs. Upon IR exposure, DDX54 acts by increased interaction with a well-defined class of pre-mRNAs that harbor introns with weak acceptor splice sites, as well as by protein-protein contacts within components of U2 snRNP and spliceosomal B complex, resulting in lower intron retention and higher processing rates of its target transcripts. Because DDX54 promotes survival after exposure to IR, its expression and/or mutation rate may impact DDR-related pathologies. Our work indicates the relevance of many uncharacterized RBPs potentially involved in the DDR.
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