DIK, a novel protein kinase that interacts with protein kinase Cδ -: Cloning, characterization, and gene analysis

A novel serine/threonine kinase, termed DIK, was cloned-using the yeast two-hybrid system to screen a cDNA library from the human keratinocyte cell line Ha-CaT with the catalytic domain of rat protein kinase C6 (PKC delta (cat)) CDNA as bait. The predicted 784-amino acid polypeptide with a calculated molecular mass of 86 kDa contains a-catalytic kinase domain and a putative regulatory domain with ankyrin-like repeats and a nuclear localization signal. Expression of DIK at the mRNA and protein level could be demonstrated in several cell lines. The dik gene is located on chromosome 21q22.3 and possesses 8 exons and 7 introns, DIK was synthesized in an in vitro transcription/translation system and expressed:as recombinant protein in bacteria, HEK, COS-7, and baculovirus-infected insect cells. In the in vitro system and in cells, but not in bacteria, various post-translationally modified forms of DIK were produced. DM was shown to exhibit protein kinase activity toward autophosphorylation and substrate phosphorylation. The interaction of PKC delta (cat) and PKC delta with DIK was confirmed by coimmunoprecipitation of the proteins from HEK cells transiently transfected with PRC delta (cat) or PKC gamma and DIK expression constructs.