Molecular association between ATR and two components of the nucleosome remodeling and deacetylating complex, HDAC2 and CHD4

Ataxia telangiectasia mutated (ATM)- and Rad3-related protein (ATR) is a ph osphatidylinositol-kinase (PIK)-related kinase that has been implicated in the response of human cells to multiple forms of DNA damage and may play a role in the DNA replication checkpoint. The purification of an ATR complex allowed identification of chromodomain-helicase-DNA-binding protein 4 (CHD4 ) as an ATR-associated protein by tandem mass spectrometric sequencing. CHD 4 (also called Mi-2 beta) is a component of a histone deacetylase-2 (HDAC2) -containing complex, the nucleosome remodeling and deacetylating (NRD) comp lex. Endogenous ATR, CHD4, and HDAC2 are shown to coimmunoprecipitate, and ATR and HDAC2 coelute through two biochemical purification steps. Other mem bers of the NRD complex, HDAC1, MTA1, and MTA2, are also detectable in ATR immunoprecipitates. ATR's association with CHD4 and HDAC2 suggests that the re may be a linkage between ATR's role in mediating checkpoints induced by DNA damage and chromatin modulation via remodeling and deacetylation.