Cell cycle-mediated structural and functional alteration of P85gag-mos protein kinase activity.
We investigated cell cycle-dependent regulation of protein kinase activity encoded by the viral mos gene by using a normal rat kidney cell line (NRK-6m2) chronically infected with a temperature-sensitive mutant (ts110) of Moloney murine sarcoma virus, which produces the P85gag-mos transforming protein. In elutriation experiments, in which cells in various phases of the cell cycle are separated based upon size, a twofold increase in the specific activity of the P85gag-mos protein kinase was observed as cells progressed from G0/G1 through S and G2/M. A three- to fourfold increase in gas-mos protein kinase specific activity relative to unsynchronized cells was observed in mitotic NRK-6m2 cells synchronized by treatment with thymidine followed by colcemid or with nocodazole alone. Interestingly, the gag-mos protein was structurally altered in mitotic cells generating a protein species moving slower than P85gag-mos in SDS-polyacrylamide gels. Our findings indicate that viral mos protein kinase activity is regulated during the cell cycle via phosphorylation. We propose that the mos transforming protein functions in a pleiotropic manner, affecting both cytoplasmic and nuclear targets.
Liu
J X
JX
Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Singh
B
B
Wlodek
D
D
Arlinghaus
R B
RB
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002453:Cell Cycle; D002469:Cell Separation; D015151:Immunoblotting; D008938:Mitosis; D017232:Oncogene Proteins v-mos; D010449:Peptide Mapping; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000032:analysis*; D051381:Rats; D015682:Retroviridae Proteins, Oncogenic / Q000032:analysis* / Q000276:immunology / Q000502:physiology
D000596:Amino Acids; D017232:Oncogene Proteins v-mos; D015682:Retroviridae Proteins, Oncogenic; D011505:Protein-Tyrosine Kinases