ACTIVITY OF C-MYC PROTEIN IS NECESSARY DURING THE FIRST 6 HOURS OF PREREPLICATIVE PERIOD IN 3T3 SWISS CELLS

Microinjection of polyclonal antibodies to the c-myc protein specifica lly inhibits in a dose-dependent manner the DNA replication only withi n the first 6 h after serum stimulation of resting 3T3 Swiss cells. Po lyclonal antibodies against separate parts of c-myc were less effectiv e than those against the whole protein. Five different monoclonal anti bodies or their mixture were without effect. Induced expression of an antisense c-myc sequence introduced into the 3T3 Swiss cells was found to markedly suppress DNA synthesis during the first 6 h of the prerep licative period. Thus, c-myc was shown to be involved in the early sta ges of the cell preparation to replication, i.e., in the cell transiti on from G(0) to G(1)