Requirement of MTA1 in ATR-mediated DNA Damage Checkpoint Function

Abstract

MTA1 (metastasis-associated protein 1), an integral component of the nucleosome remodeling and deacetylase complex, has recently been implicated in the ionizing radiation-induced DNA damage response. However, whether MTA1 also participates in the UV-induced DNA damage checkpoint pathway remains unknown. In response to UV radiation, ATR (ataxia teleangiectasia-and Rad3-related) is the major kinase activated that orchestrates cell cycle progression with DNA repair machinery by phosphorylating and activating a number of downstream substrates, such as Chk1 (checkpoint kinase 1) and H2AX (histone 2A variant X). Here, we report that UV radiation stabilizes MTA1 in an ATR-dependent manner and increases MTA1 binding to ATR. On the other hand, depletion of MTA1 compromises the ATR-mediated Chk1 activation following UV treatment, accompanied by a marked down-regulation of Chk1 and its interacting partner Claspin, an adaptor protein that is required for the phosphorylation and activation of Chk1 by ATR. Furthermore, MTA1 deficiency decreases the induction of phosphorylated H2AX (referred to as ␥-H2AX) and ␥-H2AX focus formation after UV treatment. Consequently, depletion of MTA1 results in a defect in the G 2 -M checkpoint and increases cellular sensitivity to UV-induced DNA damage. Thus, MTA1 is required for the activation of the ATR-Claspin-Chk1 and ATR-H2AX pathways following UV treatment, and the noted abrogation of the DNA damage checkpoint in the MTA1-depleted cells may be, at least in part, a consequence of dysregulation of the expression of these two pathways. These findings suggest that, in addition to its role in the repair of double strand breaks caused by ionizing radiation, MTA1 also participates in the UV-induced ATR-mediated DNA damage checkpoint pathway.MTA1 (metastasis-associated protein 1), the founding member of the MTA 2 family, is widely up-regulated in human cancers and plays an important role in tumorigenesis, tumor invasion, and metastasis (1-3). As a dual function coregulator (3, 4), MTA1 functions not only as a transcriptional repressor of estrogen receptor-␣ (5), BRCA1 (breast cancer type 1 susceptibility protein) (6), Six3 (7), and p21 WAF11 (8) genes but also as a transcriptional activator via interacting with RNA polymerase II on the BCAS3 (breast cancer-amplified sequence 3) (9) and Pax5 (paired box gene 5) (10) promoters. The co-repressor versus co-activator activity of MTA1 might be influenced by its binding partners on the promoter region of various genes. In addition to its paramount role in cancer and coregulator biology, emerging evidence suggests that MTA1 is a DNA damageresponsive protein and facilitates DNA double strand break (DSB) repair following ionizing radiation (IR) treatment (11,12). In support of these findings, recent studies have demonstrated that MTA1 regulates p53-dependent and -independent DNA repair processes following IR treatment by modulating p53-p53R2 and p21 WAF1 -proliferating cell nuclear antigen pathways, respectively (8, 13). However, the new functions and rel...

Metastasis-associated Protein 1 Drives Tumor Cell Migration and Invasion through Transcriptional Repression of RING Finger Protein 144A

“…siRNA and Transfections-Specific siRNAs targeting human MTA1 and RNF144A were purchased from Dharmacon (Lafayette, CO), and the specificity of these MTA1 siRNAs has been verified previously (28). The transfection of siRNA was performed twice at 24-h intervals with Oligofectamine TM reagent (Invitrogen) according to the manufacturer's protocol.…”

MTA1 promotes cell proliferation via DNA damage repair in epithelial ovarian cancer

“…Li et al (2010b) suggested an inherent role of the MTA1-p53-p53R2 pathway in the DNA damage response in cancer cells. In addition, the presence of an additional p53-independent role of MTA1 in the DNA damage response, that acts in part by modulating the p21(WAF1)-PCNA pathway, has also been identified.…”

“…MTA1 has recently been recognized as an effective DNA damage response protein, linking 2 previously unconnected NuRD complex and DNA damage response pathways (Li et al, 2010b). Li et al (2010b) suggested an inherent role of the MTA1-p53-p53R2 pathway in the DNA damage response in cancer cells.…”

“…Although it is known that MTA1 overexpression results in increased DNA DSB repair and decreased DNA damage sensitivity following IR treatment in p53-null cells (Li et al, 2010b), no studies have explored the role of MTA1 in the DNA damage response of ovarian cancer cells. Therefore, because platinum-based chemotherapy following surgical tumor debulking is the standard treatment for advanced EOC, and IR is ubiquitously used in the therapy of many cancers, we investigated the possible therapeutic role of MTA1 in ovarian cancer cells following CDDP and IR treatment.…”

“…Specifically, MTA1 is involved in the ionizing radiation (IR)-induced DNA damage response and the ultraviolet-induced DNA damage checkpoint pathway (Li and Kumar, 2010;Lan et al, 2010). Moreover, MTA1 regulates DNA repair in a p53-dependent and -independent manner and facilitates the repair of DNA doublestrand breaks (DSBs) resulting from exposure to genotoxic stress (Li et al, 2010b).…”