Phosphorylation of v-mos Ser 47 by the mitotic form of p34cdc2.
P85gag-mos is hyperphosphorylated during mitosis in normal rat kidney (NRK) cells transformed by Moloney murine sarcoma virus ts110. We now report that P85gag-mos is phosphorylated in vitro by the mitotic form of the cdc2 kinase (p34cdc2, known as M-phase kinase) derived from virus-transformed cells. The major site of P85gag-mos phosphorylation by the M-phase kinase in vitro lies within the amino-terminal portion of the viral mos protein sequence spanning residues 45-53, as determined by tryptic peptide mapping. A synthetic peptide corresponding to amino acids 37-55 of v-mos was specifically phosphorylated by the M-phase kinase, whereas v-mos peptides either lacking Ser 47 or substituted with Ala at residue 47 were not phosphorylated. Protein sequencing analyses established that the M-phase kinase specifically phosphorylates Ser 47. Tryptic phosphopeptide mapping of the in vivo-phosphorylated gag-mos protein from mitotic cells indicated that the 45-53 v-mos region was also phosphorylated within mitotic cells. These findings demonstrate that the M-phase kinase phosphorylates the viral mos protein at Ser 47. These results were unexpected in view of earlier reports regarding cdc2 kinase activation/stabilization by the c-mos kinase in maturing oocytes.
Bai
W L
WL
Department of Molecular Pathology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Singh
B
B
Karshin
W L
WL
Shonk
R A
RA
Arlinghaus
R B
RB
D000818:Animals; D016203:CDC2 Protein Kinase / Q000502:physiology*; D002461:Cell Line, Transformed; D015681:Fusion Proteins, gag-onc / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D017232:Oncogene Proteins v-mos; D010449:Peptide Mapping; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism*
D015681:Fusion Proteins, gag-onc; D017232:Oncogene Proteins v-mos; D015682:Retroviridae Proteins, Oncogenic; D011505:Protein-Tyrosine Kinases; D016203:CDC2 Protein Kinase