PITALRE, a nuclear CDC2-related protein kinase that phosphorylates the retinoblastoma protein in vitro.

Abstract

Members of the cell division cycle 2 (CDC2) family of kinases play a pivotal role in the regulation of the eukaryotic cell cyde. In this communication, we report the isolation of a cDNA that encodes a CDC2-related human protein kinase temporarily designated PITALRE for the characteristic Pro-Ile-Thr-Ala-Leu-Arg-Glu motif. Its deduced amino acid sequence is 47% identical to that of the human cholinesterase-related cell division controller (CHED) kinase, which is required during hematopoiesis, and 42% identical to the Saccharomyces cerewasle SGV1 gene product, a putative kinase involved in the response to pheromone via its guanine nucleotide-binding protein a subunit. PITALRE expression is ubiquitous, but its expression levels are different in various human tissues. PITALRE is an =43-kDa protein that associates with three cellular polypeptides of 80, 95, and 155 kDa. PITALRE is lad primarily to the nucleus. In addition, we have identified a retinoblastoma protein kinase activity associated with PITALRE Immunocomplexes that cannot phosphorylate histone Hi, suggesting that the target phosphorylation site of PITALRE differs from that of CDC2 kinase. Interestingly, the retinoblastoma kinase activity associated with PITALRE does not oscillate during the cell cycle.The cell cycle in eukaryotes is regulated by a sequence of restriction points. In yeast, the first restriction point occurs during the G1 phase prior to the DNA synthesis and the second occurs before the initiation of mitosis. In Saccharomyces cerevisiae, the cell division cycle 28 (CDC28) kinase controls both restriction points through association with the CLN cyclins in G1 and with CLB cyclins in G2/M (1). In vertebrate cells, the regulatory mechanisms involved in cell cycle progression are more complex. CDC2 kinase, in association with cyclin B, appears to be a universal regulator of the eukaryotic entry into mitosis. However, in G1, just before the onset of DNA synthesis, cyclin-dependent kinase 2 (CDK2), but not CDC2, is required (2, 3). Additional mammalian CDC2-related kinases have been isolated that share >40% identity at the amino acid level (4)(5)(6)(7)(8)(9)(10)(11) This indicates that CDK4-cyclin D complexes possess a different phosphorylation specificity than the CDC2 kinase. Nevertheless, no kinase activity has been detected in CDK4 immunocomplexes (12). The association of CDK5 with cyclins D1/D3 and with proliferating cell nuclear antigen (PCNA) suggests a role for this kinase in the cell cycle (13). However, the high levels of expression of cdk5 found in neurons, cells no longer dividing, indicate a role for CDK5 in terminally differentiated cells (11). The study of CDC2 and CDC2-related kinases over the past few years has revealed a key role for these kinases in the regulation of the cell cycle. Most recently, an involvement in differentiation processes has also been proposed (8,11).With the aim of isolating additional putative controllers of the mammalian cell cycle, we performed a combination of PCR amplification and low-stringency ...

Alternative splicing of the human CDC25B tyrosine phosphatase. Possible implications for growth control?

“…Twò PISLRE', CDK-related proteins that are probable splice variants of the same gene have been cloned (Brambilla and Draetta, 1994;Grana et al, 1994) and a cyclin E splicing variant that lacks 49 amino-acids within the cyclin box and is therefore unable to bind cdk2 has been found in several cell lines (Sewing et al, 1994). Alternate splicing resulting in the production of a novel cyclin D1 transcript has also been identi®ed and appears to be modulated by A/G polymorphism located at the splice donor region of exon 4 (Betticher et al, 1995).…”

Upregulation of cyclin T1/CDK9 complexes during T cell activation

“…Cloning of the subunits of PTEFb has revealed that it is a cyclin/CDK pair (Peng et al, 1998a;Wei et al, 1998;Zhu et al, 1997). The small subunit of Drosophila P-TEFb was cloned using sequence information obtained from the puri®ed protein and was found to be the homolog of the human CDC2-related kinase PI-TALRE (GranÄ a et al, 1994a). We have reported previously that PITALRE is a primarily nuclear Ser/ Thr-Pro-directed kinase (Garriga et al, 1996b) with activity that is not cell cycle regulated in HeLa and ML-1 (GranÄ a et al, 1994a).…”

“…The small subunit of Drosophila P-TEFb was cloned using sequence information obtained from the puri®ed protein and was found to be the homolog of the human CDC2-related kinase PI-TALRE (GranÄ a et al, 1994a). We have reported previously that PITALRE is a primarily nuclear Ser/ Thr-Pro-directed kinase (Garriga et al, 1996b) with activity that is not cell cycle regulated in HeLa and ML-1 (GranÄ a et al, 1994a). Initial studies found most of the active PITALRE in high molecular weight complexes containing a number of unidenti®ed proteins.…”

Physical interaction between CDK9 and B-Myb results in suppression of B-Myb gene autoregulation

“…CDK9 (previously named PITALRE) is a cdc2-like kinase (GranÄ a et al, 1994;De Falco and Giordano, 1998). It di ers from other cdks because its expression is not cell cycle regulated and does not appear to be required during the cell cycle.…”