MOLECULAR-CLONING OF PISSLRE, A NOVEL PUTATIVE MEMBER OF THE CDK FAMILY OF PROTEIN SERINE THREONINE KINASES/

Several members of the cdk family of protein kinases are involved in t he regulation of the eukaryotic cell cycle. Using a PCR-based strategy we have screened different human tumor cell lines for cdk-related cDN As. One clone isolated from the bladder carcinoma cell line RT112 enco des a novel protein kinase named PISSLRE, based on its predicted seque nce at the conserved PSTAIRE motif. PISSLRE showed 50% amino acid iden tity with the previously isolated p58(KGTA). PISSLRE contained all the structural elements featured by cyclin dependent kinases, including a proline in the PSTAIRE motif, which might be important for cyclin bin ding. PISSLRE was found expressed as 2.0 kb messenger RNA in a variety of human cell lines. Its expression was not restricted to tumor cells as it was detectable also in normal fibroblasts. In adult tissues, PI SSLRE mRNA showed the highest expression in lung, liver and kidney. Th e broad expression pattern in adult tissues might suggest that PISSLRE could be involved in processes distinct from cell proliferation.