Cell-cycle-dependent expression of the STK-1 gene encoding a novel murine putative protein kinase

We have cloned a novel putative serine/threonine kinase-encoding gene, designated STK-1, from murine embryonic stem (ES) cell and testis cDNA libraries. The kinase most closely related to STK-1 is Xenopus laevis XLP46 protein kinase which shows 71% amino-acid identity to STK-1 between their kinase domains. Nevertheless, STK-1 is conserved throughout phylogeny with hybridizing sequences being detected in DNA from mammals, amphibians, insects and yeast. STK-1 mRNA is detected in testis, intestine and spleen, tissues that contain a large number of proliferating cells, but not in other tissues. All cell lines tested expressed STK-1 mRNA with levels being dependent upon proliferation rates. In NIH 3T3 cells, STK-1 is expressed in a cell-cycle-dependent fashion. These findings suggest a role for STK-1 in cell growth