Article

Dual recognition of phosphoserine and phosphotyrosine in histone variant H2A.X by DNA damage response protein MCPH1

Departments of Biochemistry and Molecular Biology, Laboratory Medicine and Pathology, and Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 08/2012; 109(36):14381-6. DOI: 10.1073/pnas.1212366109
Source: PubMed

ABSTRACT

Tyr142, the C-terminal amino acid of histone variant H2A.X is phosphorylated by WSTF (Williams-Beuren syndrome transcription factor), a component of the WICH complex (WSTF-ISWI chromatin-remodeling complex), under basal conditions in the cell. In response to DNA double-strand breaks (DSBs), H2A.X is instantaneously phosphorylated at Ser139 by the kinases ATM and ATR and is progressively dephosphorylated at Tyr142 by the Eya1 and Eya3 tyrosine phosphatases, resulting in a temporal switch from a postulated diphosphorylated (pSer139, pTyr142) to monophosphorylated (pSer139) H2A.X state. How mediator proteins interpret these two signals remains a question of fundamental interest. We provide structural, biochemical, and cellular evidence that Microcephalin (MCPH1), an early DNA damage response protein, can read both modifications via its tandem BRCA1 C-terminal (BRCT) domains, thereby emerging as a versatile sensor of H2A.X phosphorylation marks. We show that MCPH1 recruitment to sites of DNA damage is linked to both states of H2A.X.

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    • "To date, BRCT 2 domains of three mammalian proteins— MCPH1, PTIP, and MDC1—have been found to specifically recognize the primary mark of DNA damage, gH2AX (Yan et al., 2011; Stucki et al., 2005; Singh et al., 2012). Our data show unambiguously that this is a property shared Figure 3. Co-localization of pATM Is Disrupted in 53BP1-BRCT 2 Phospho-Binding Mutants (A) HeLa cells were reverse transfected with 53BP1 siRNA. "
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    • "BRCT2/3 domains have been shown to bind to E2F1 to form a complex able to transactivate BRCA1 and CHK1 (Yang et al., 2008). Interactions between MCPH1 BRCT2/3 domains and Cdc27, a subunit of the anaphasepromoting complex (Singh et al., 2012b), and a phosphorylated domain of H2A.X have also been reported (Singh et al., 2012a). On the other hand, a truncated MCPH1 protein lacking BRCT2/3, is able to complement the defective chromosome condensation in human MCPH1-deficient cells (Gavvovidis et al., 2012), indicating that these domains are dispensable for this function. "
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    • "Neither MDC1 nor MCPH1 is able to bind H2A.X-derived peptides carrying the Y142ph mark alone. Interestingly , MCPH1 is able to bind doubly phosphorylated peptides (phosphorylated at Y142 and S139) with its tandem BRCT domains, however its affinity is substantially higher when the substrate is phosphorylated only at S139, whereas MDC1 is unable to bind doubly phosphorylated peptides [104]. In a recent report [105], another DNA damage-dependent histone phosphorylation mark was characterized in yeast. "
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