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Sumoylation of MDC1 is important for proper DNA damage response.

ABSTRACT: 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.

SUBMITTER: Luo K

PROVIDER: S-EPMC3395099 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Oligomerization of MDC1 protein is important for proper DNA damage response.

Project description:Mediator of DNA damage checkpoint 1 (MDC1) plays an important role in the DNA damage response (DDR). MDC1 functions as a mediator protein and binds multiple proteins involved in different aspects of the DDR. However, little is know about the organization of MDC1 complexes. Here we show that ataxia telangiectasia, mutated (ATM) phosphorylates MDC1 at Thr-98 following DNA damage, which promotes its oligomerization. Oligomerization of MDC1 is important for the accumulation of MDC1 complex at the sites of DNA damage. Mutation of Thr-98 (T98A) would abolish its oligomerization and result in a defect in DNA damage checkpoint activation and increased sensitivity to irradiation. Taken together, these results suggest that the oligomerization of MDC1 plays an important role in DDR and help understand the formation of proteins complexes at the sites of DNA damage.

| S-EPMC3151064 | biostudies-literature

DNA Damage Response-Independent Role for MDC1 in Maintaining Genomic Stability.

Project description:MDC1 is a central player in checkpoint activation and subsequent DNA repair following DNA damage. Although MDC1 has been studied extensively, many of its known functions, to date, pertain to the DNA damage response (DDR) pathway. Herein we report a novel function of phosphorylated MDC1 that is independent of ATM and DNA damage and is required for proper mitotic progression and maintenance of genomic stability. We demonstrate that MDC1 is an in vivo target of Plk1 and that phosphorylated MDC1 is dynamically localized to nuclear envelopes, centrosomes, kinetochores, and midbodies. Knockdown of MDC1 or abrogation of Plk1 phosphorylation of MDC1 causes a delay of the prometaphase-metaphase transition. It is significant that mice with reduced levels of MDC1 showed an elevated level of spontaneous tumors in aged animals. Our results demonstrate that MDC1 also plays a fundamentally significant role in maintenance of genomic stability through a DDR-independent pathway.

| S-EPMC5394279 | biostudies-literature

CK2 phosphorylation-dependent interaction between aprataxin and MDC1 in the DNA damage response.

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| S-EPMC2836575 | biostudies-literature

Distinct versus overlapping functions of MDC1 and 53BP1 in DNA damage response and tumorigenesis.

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| S-EPMC2396806 | biostudies-other

Nucleolin participates in DNA double-strand break-induced damage response through MDC1-dependent pathway.

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| S-EPMC3492271 | biostudies-literature

ID3 regulates the MDC1-mediated DNA damage response in order to maintain genome stability.

Project description:MDC1 plays a critical role in the DNA damage response (DDR) by interacting directly with several factors including γ-H2AX. However, the mechanism by which MDC1 is recruited to damaged sites remains elusive. Here, we show that MDC1 interacts with a helix-loop-helix (HLH)-containing protein called inhibitor of DNA-binding 3 (ID3). In response to double-strand breaks (DSBs) in the genome, ATM phosphorylates ID3 at serine 65 within the HLH motif, and this modification allows a direct interaction with MDC1. Moreover, depletion of ID3 results in impaired formation of ionizing radiation (IR)-induced MDC1 foci, suppression of γ-H2AX-bound MDC1, impaired DSB repair, cellular hypersensitivity to IR, and genomic instability. Disruption of the MDC1-ID3 interaction prevents accumulation of MDC1 at sites of DSBs and suppresses DSB repair. Thus, our study uncovers an ID3-dependent mechanism of recruitment of MDC1 to DNA damage sites and suggests that the ID3-MDC1 interaction is crucial for DDR.MDC1 is a key component of the DNA damage response and interacts with several factors such as γ-H2AX. Here the authors show that MDC1 interacts with ID3, facilitating MDC1 recruitment to sites of damage and repair of breaks.

| S-EPMC5638908 | biostudies-literature

MDC1 cleavage by caspase-3: a novel mechanism for inactivating the DNA damage response during apoptosis.

Project description:Recently, we identified the "apoptotic ring," containing phosphorylated histone H2AX (γ-H2AX), as an early chromatin modification during apoptosis. Because γ-H2AX initiates the DNA damage response (DDR), we tested whether the apoptotic H2AX response leads to the full recruitment of the DDR factors that normally coordinate DNA repair and cell-cycle checkpoints. We show that the apoptotic H2AX response does not recruit the DDR factors because MDC1 (mediator of DNA damage checkpoint protein 1), which normally binds to γ-H2AX in response to DNA damage and amplifies the DDR, is cleaved by caspase-3. This cleavage separates the BRCT and FHA domains of MDC1 and constitutes a novel mechanism for the inactivation of DNA repair in apoptotic cells. Also, we show that downregulation of MDC1 increases the apoptotic response to TRAIL. Together, these results implicate MDC1 in the cellular apoptotic response.

| S-EPMC3032822 | biostudies-literature

Author Correction: ID3 regulates the MDC1-mediated DNA damage response in order to maintain genome stability.

Project description:This Article contains errors in Fig. 3, Fig. 4 and Fig. 7, for which we apologize. In Fig. 3, panel 'b', the 0.5 hour time point after Ku55933 treatment images were inadvertently replaced with duplicates of the 3 hour time point after Ku55933 treatment images in Fig. 3b. Additionally, in panel 'b', the 0.5 hour time point after Nu7026 treatment images were inadvertently replaced with duplicates of the 180 min time point after siMDC1 treatment images in Fig. 3d. In Fig. 4, panel 'g', RNF168 foci in U2OS cell images were inadvertently replaced with duplicates of RNF168 foci in HeLa cell images in Fig. 4f. In Fig. 7, panel 'b', the DAPI images 0.5 hours after IR under siID3 treatment were inadvertently replaced with DAPI images of a different field of view from the same experiment. Additionally, in panel 'i', the shID3 mock-treated GFP-ID3 cells image was inadvertently replace with duplications of the shID3 mock-treated GFP-ID3 cells image in Fig. 7g.

| S-EPMC5989224 | biostudies-literature

Mdb1, a fission yeast homolog of human MDC1, modulates DNA damage response and mitotic spindle function.

Project description:During eukaryotic DNA damage response (DDR), one of the earliest events is the phosphorylation of the C-terminal SQ motif of histone H2AX (H2A in yeasts). In human cells, phosphorylated H2AX (γH2AX) is recognized by MDC1, which serves as a binding platform for the accumulation of a myriad of DDR factors on chromatin regions surrounding DNA lesions. Despite its important role in DDR, no homolog of MDC1 outside of metazoans has been described. Here, we report the characterization of Mdb1, a protein from the fission yeast Schizosaccharomyces pombe, which shares significant sequence homology with human MDC1 in their C-terminal tandem BRCT (tBRCT) domains. We show that in vitro, recombinant Mdb1 protein binds a phosphorylated H2A (γH2A) peptide, and the phospho-specific binding requires two conserved phospho-binding residues in the tBRCT domain of Mdb1. In vivo, Mdb1 forms nuclear foci at DNA double strand breaks (DSBs) induced by the HO endonuclease and ionizing radiation (IR). IR-induced Mdb1 focus formation depends on γH2A and the phospho-binding residues of Mdb1. Deleting the mdb1 gene does not overtly affect DNA damage sensitivity in a wild type background, but alters the DNA damage sensitivity of cells lacking another γH2A binder Crb2. Overexpression of Mdb1 causes severe DNA damage sensitivity in a manner that requires the interaction between Mdb1 and γH2A. During mitosis, Mdb1 localizes to spindles and concentrates at spindle midzones at late mitosis. The spindle midzone localization of Mdb1 requires its phospho-binding residues, but is independent of γH2A. Loss of Mdb1 or mutating its phospho-binding residues makes cells more resistant to the microtubule depolymerizing drug thiabendazole. We propose that Mdb1 performs dual roles in DDR and mitotic spindle regulation.

| S-EPMC4013092 | biostudies-literature

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

Project description:NFBD1/MDC1 is involved in DNA damage checkpoint signaling and DNA repair. NFBD1 binds to the chromatin component ?H2AX at sites of DNA damage, causing amplification of ataxia telangiectasia-mutated gene (ATM) pathway signaling and recruitment of DNA repair factors. Residues 508-995 of NFBD1 possess transactivation activity, suggesting a possible role of NFBD1 in transcription. Furthermore, NFBD1 influences p53-mediated transcription in response to adriamycin. We sought to determine the role of NFBD1 in ionizing radiation (IR)-responsive transcription and if NFBD1 influences transcription independently of p53. Using microarray analysis, we identified genes altered upon NFBD1 knockdown. Surprisingly, most NFBD1 regulated genes are regulated in both the absence and presence of IR, thus pointing toward a novel function for NFBD1 outside of the DNA damage response. Furthermore, NFBD1 knockdown regulated genes mostly independent of p53 knockdown. These genes are involved in pathways including focal adhesion signaling, carbohydrate metabolism, and insulin signaling. We found that CAV1 and CAV2 mRNA and protein levels are reduced by both NFBD1 knockdown and knockout independently of IR and p53. NFBD1-depleted cells exhibit some similar phenotypes to Cav1-depleted cells. Furthermore, like Cav1-depletion, NFBD1 shRNA increases Erk phosphorylation. Thus, Cav1 could act as a mediator of the DNA-damage independent effects of NFBD1 in mitogenic signaling.

| S-EPMC3901581 | biostudies-literature

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