Regulated expression of a cell division control-related protein kinase during development.

Protein kinases are important signaling molecules that are known constituents of cellular pathways critical for normal cellular growth and development. We have recently identified a new protein kinase, p58, which contains a large domain that is highly homologous to the cell division control p34cdc2 protein kinase. This new cell division control-related protein kinase was originally identified as a component of semipurified galactosyltransferase; thus, it has been denoted galactosyltransferase-associated protein kinase. In vitro, this protein kinase has been shown to phosphorylate a number of substrates, including histone H1, casein, and galactosyltransferase. In vivo, we have found that this protein kinase affects galactosyltransferase enzyme activity and that it is apparently involved in some aspect of normal cell cycle regulation. In this report, we find that the p58 gene is evolutionarily well conserved and expressed ubiquitously, but to varying extents, in adult tissues. In developmentally staged embryos, p58 expression was elevated early in embryogenesis and then decreased dramatically. In the murine submandibular gland, p58 expression was elevated between day 14 and day 16 post coitus. Expression in the submandibular gland appeared to parallel the proliferation and differentiation of specific cell types as judged by in situ hybridization. These studies indicate that the p58 protein kinase may have a critical function during normal embryonic development and that this protein kinase continues to be expressed in differentiated adult tissues.