REPLICATION OF SATELLITE DNA IN THE KANGAROO RAT CELLS DURING INHIBITION OF PROTEIN SYNTHESIS

Abstract

The effects of inhibition of protein synthesis by puromycin on the replication of satellite DNA in the Kangaroo rat cells, D. ordii were studied. In all experiments, cells were partially synchronized at the beginning of the S phase. When protein synthesis is inhibited by puromycin, overall rate of DNA synthesis in the S phase cells is reduced. Replication of satellite DNA which replicates later in the S phase is equally sensitive to puromycin as early replicating other bulk of DNA. The reduction in the overall rate of DNA synthesis was further examined at the level of replicons by using DNA fiber autoradiography. The rate of DNA chain elongation within individual replicons is slightly reduced in puromycin-treated cells. However, this reduction in the rate of DNA chain elongation at the level of replicons does not entirely account for the inhibition of overall rate of DNA synthesis per cell. When cells were labeled for longer periods in the presence of puromycin, the formation of long radioactive pieces of DNA was prevented and small pieces were accumulated. The failure in the formation of long radioactive pieces may be due to the inability to activate replicons or their clusters which are not yet activated. These results indicate that inhibition of satellite DNA replication does require protein synthesis in similar manner as observed in the other bulk of nuclear DNA.