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VCP maintains nuclear size by regulating the DNA damage-associated MDC1-p53-autophagy axis in Drosophila.

ABSTRACT: The maintenance of constant karyoplasmic ratios suggests that nuclear size has physiological significance. Nuclear size anomalies have been linked to malignant transformation, although the mechanism remains unclear. By expressing dominant-negative TER94 mutants in Drosophila photoreceptors, here we show disruption of VCP (valosin-containing protein, human TER94 ortholog), a ubiquitin-dependent segregase, causes progressive nuclear size increase. Loss of VCP function leads to accumulations of MDC1 (mediator of DNA damage checkpoint protein 1), connecting DNA damage or associated responses to enlarged nuclei. TER94 can interact with MDC1 and decreases MDC1 levels, suggesting that MDC1 is a VCP substrate. Our evidence indicates that MDC1 accumulation stabilizes p53A, leading to TER94^K2A-associated nuclear size increase. Together with a previous report that p53A disrupts autophagic flux, we propose that the stabilization of p53A in TER94^K2A-expressing cells likely hinders the removal of nuclear content, resulting in aberrant nuclear size increase.

SUBMITTER: Chang YC

PROVIDER: S-EPMC8275807 | biostudies-literature |

REPOSITORIES: biostudies-literature

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NFBD1/MDC1 regulates Cav1 and Cav2 independently of DNA damage and p53.

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Project description: Not available

| S-EPMC8923128 | biostudies-literature

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Project description:The role of MDC1 in the DNA damage response has been extensively studied, however, its impact on other cellular processes is not well understood. Here, we describe a role for MDC1 in transcription by regulating the activity of the RNAPolymerase II (RNAPII). Depletion of MDC1 caused a genome-wide reduction in the abundance of actively engaged RNAPII elongation complexes throughout the gene body of protein coding genes under unperturbed conditions. Decreased engaged RNAPII subsequently alters the assembly of the spliceosome complex on chromatin, leading to defects in pre-mRNA splicing. Mechanistically, the S/TQ domain of MDC1 modulates RNAPII-mediated transcription. Upon genotoxic stress, MDC1 promotes the abundance of engaged RNAPII complexes at DNA breaks, thereby stimulating nascent transcription at the damaged sites. Of clinical relevance, cancer cells lacking MDC1 display hypersensitivity to RNAPII inhibitors. Overall, we unveil a previously uncharacterized role of MDC1 in RNAPII-mediated transcription with potential implications for cancer treatment.

2022-11-24 | GSE215990 | GEO

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Sumoylation of MDC1 is important for proper DNA damage response.

Project description:In response to DNA damage, many DNA damage factors, such as MDC1 and 53BP1, redistribute to sites of DNA damage. The mechanism governing the turnover of these factors at DNA damage sites, however, remains enigmatic. Here, we show that MDC1 is sumoylated following DNA damage, and the sumoylation of MDC1 at Lys1840 is required for MDC1 degradation and removal of MDC1 and 53BP1 from sites of DNA damage. Sumoylated MDC1 is recognized and ubiquitinated by the SUMO-targeted E3 ubiquitin ligase RNF4. Mutation of the MDC1 Lys 1840 (K1840R) results in impaired CtIP, replication protein A, and Rad51 accumulation at sites of DNA damage and defective homologous recombination (HR). The HR defect caused by MDC1K1840R mutation could be rescued by 53BP1 downregulation. These results reveal the intricate dynamics governing the assembly and disassembly of DNA damage factors at sites of DNA damage for prompt response to DNA damage.

| S-EPMC3395099 | biostudies-literature

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