CLONING OF MURINE CDK9 PITALRE AND ITS TISSUE-SPECIFIC EXPRESSION IN DEVELOPMENT/

The cdc2-family of serine/threonine kinases and their binding partners recently were implicated in developmental roles. We previously cloned a cdc2-related kinase, cdk9/PITALRE, that is able to phosphorylate th e retinoblastoma protein in vitro. We describe here the cloning and th e characterization of the mouse homolog of cdk9/PITALRE. The murine cD NA is 98% identical with humans and is expressed at high levels in bra in and kidney tissues. The kinase activity and protein expression of c dk9/PITALRE were highest in terminally differentiated tissues such as the muscle and brain. In situ immunohistology and immunofluorescence d etected cdk9/PITALRE protein not only within terminally differentiated cells such as muscle and neuronal cells but also in proliferating cel ls. C2C12 and P19 cells induced to differentiate along muscle and neur al lineages peaked in cdk9/PITALRE kinase activity at the end of diffe rentiation. These results suggest that, among other roles, cdk9/PITALR E plays a role not unlike cdk5 in the differentiation of certain cell types. J. Cell. Physiol. 177:206-213, 1998. (C) 1998 Wiley-Liss, Inc.