CK2-dependent phosphorylation of the Brg1 chromatin remodeling enzyme occurs during mitosis

Abstract

ABSTRACTBrg1 (Brahma related gene 1) is one of two mutually exclusive ATPases that can act as the catalytic subunit of mammalian SWI/SNF chromatin remodeling enzymes that facilitate utilization of the DNA in eukaryotic cells. Brg1 is a phospho-protein and its activity is regulated by specific kinases and phosphatases. Previously, we showed that Brg1 interacts with and is phosphorylated by casein kinase 2 (CK2) in a manner that regulates myoblast proliferation. Here we demonstrate that the Brg1-CK2 interaction occurred during mitosis in embryonic somites and in primary myoblasts derived from satellite cells isolated from muscle tissue. The interaction of CK2 activity with Brg1 and the incorporation of a number of other subunits into the mSWI/SNF enzyme complex were independent of CK2 enzymatic activity. CK2-mediated hyperphosphorylation of Brg1 was observed in mitotic cells derived from multiple cell types and organisms, suggesting functional conservation across tissues and species. The mitotically hyperphosphorylated form of Brg1 was localized with soluble chromatin, demonstrating that CK2-mediated phosphorylation of Brg1 is associated with specific partitioning of Brg1 within sub-cellular compartments. Thus CK2 acts a mitotic kinase that regulates Brg1 phosphorylation and sub-cellular localization.HIGHLIGHTSInteractions between CK2 and the Brg1 chromatin remodeling enzyme occur during mitosisCK2-Brg1 interactions are independent of CK2 catalytic activityCK2-mediated phosphorylation of Brg1 is a mitotic eventCK2-mediated phosphorylation of Brg1 is conserved across mammalian cell typesThe mitotically hyperphosphorylated form of Brg1 is localized with soluble chromatin