Functions of the mos oncogene family and associated gene products.

The mos oncogene present in Moloney murine sarcoma virus is one of the oldest known oncogenes, yet the identification of its biochemical function both in transformation and as a cellular proto-oncogene has been elusive. Only recently have low levels of c-mos transcripts been detected in a specific group of mouse tissues. The c-mos gene is implicated in tumorigenicity by its activation by the insertion of the intracisternal A particle genome in a mouse plasmacytoma. The murine c-mos gene is capable of oncogenic transformation when placed under the regulatory control of a long terminal repeat. The acquisition of the v-mos gene generated the transformation-competent Moloney murine sarcoma virus and several related strains. Myeloproliferative sarcoma virus is unique among the v-mos containing viruses in its ability to induce splenic foci and myeloproliferation in vivo in addition to the transformation of fibroblasts. The v-mos gene product, termed p37mos, is a cytoplasmic protein recently shown to possess serine kinase activity in immune complexes. Autophosphorylation of the mos gene product is not necessary for its biological activity as exemplified by the protein HT1-MSV which lacks phosphoserine residues. A transcriptional regulatory property has been attributed to the v-mos gene product during infection, which may play an essential role in subsequent transformation.