Abstract
Human prk encodes a novel protein serine/threonine kinase capable of strongly phosphorylating casein but not histone H1 in vitro. prk expression is tightly regulated at various levels during different stages of the cell cycle in lung fibroblasts. The Prk kinase activity is relatively low during mitosis, G1, and G1/S, and peaks during late S and G2 stages of the cell cycle. Recombinant human Prk expressed through the baculoviral vector system is capable of phosphorylating Cdc25C, a positive regulator for the G2/M transition. Human prk shares significant sequence homology with Saccharomyces cerevisiae CDC5 and Drosophila melanogaster polo, both of which are essential for mitosis and meiosis. Full-length prk transcripts greatly potentiate progesterone-induced meiotic maturation of Xenopus laevis oocytes. On the other hand, antisense prk transcripts significantly delay and reduce the rate of oocyte maturation. When expressed in a CDC5 mutant strain of S. cerevisiae, human Prk, but not a deletional mutant protein, fully rescues the temperature-sensitive phenotype of the budding yeast. Taken together, prk may represent a new protein kinase, playing an important role in regulating the onset and/or progression of mitosis in mammalian cells.
Highlights
Cyclin-dependent kinases (CDKs)1 control many phosphorylation events during the cell cycle, and are indispensable for eukaryotic cell division [1, 2]
The prk transcript level was significantly elevated at the G1/S junction, peaking at late S and G2 stages of the cell cycle
CDKs were the first family of well documented protein kinases shown to play a major role in the regulation of G1, G1/S, and G2/M phase checkpoints [1,2,3,4,5,6]
Summary
Cyclin-dependent kinases (CDKs)1 control many phosphorylation events during the cell cycle, and are indispensable for eukaryotic cell division [1, 2]. The Prk kinase activity is relatively low during mitosis, G1, and G1/S, and peaks during late S and G2 stages of the cell cycle. Human A549 cells [21] were arrested at different stages of the cell cycle as described under “Experimental Procedures.” Fig. 1A shows that a low level of prk transcript was present in G1 cells (lane 3).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
