RETINOBLASTOMA ANTIONCOGENE IS INVOLVED IN THE INHIBITION OF MYOGENESIS BY POLYOMAVIRUS LARGE T-ANTIGEN

The expression of polyomavirus large T antigen in stably transfected C 2 myoblast cells inhibits terminal differentiation without inducing a transformed phenotype. In the present work, we report on the lifting o f this inhibition by a mutation that prevents polyomavirus large T ant igen from binding to the product of the retinoblastoma susceptibility gene (p105 RB). In contrast with cells containing wild-type large T, t hose with the Rb binding site mutant large T showed the same up-regula tion of myosine heavy chain and myogenin mRNA expression as control ce lls. Furthermore, we correlate the cell cycle alteration induced by po lyomavirus large T antigen expression with the inability of the cells to undergo terminal differentiation.