Regulation of the transcription factor, CTCF, by phosphorylation with protein kinase CK2.

CTCF is a transcription factor involved in various aspects of gene regulation. We previously reported that CTCF function is modulated by protein kinase CK2. In this report we investigate further the role of CK2 in regulating the transcriptional properties of CTCF. We demonstrate that coexpression of CTCF with CK2 switches function of CTCF from repressor to activator. The non-phosphorylatable mutant increases repression by CTCF and potentiates the growth-suppressive ability of the protein, whereas the phospho-mimetic mutant behaves in the opposite fashion. Mutation of the individual serines reveals that Serine 612 is a critical residue in regulation of CTCF by CK2.