Replicative activity of histone-deficient SV40 chromatin.

Histone-deficient SV40 chromatin, selectively radiolabeled in the DNA following the addition of cycloheximide to infected monkey cells, was compared with the normal 55S viral chromatin for its ability to serve as a template for a subsequent round of replication. After the removal of cycloheximide, the 26S histone-deficient SV40 chromatin was converted to apparently normal 55S chromatin. During this conversion, the chromatin which sedimented at 26-40S failed to replicate whereas the 44-55S chromatin contained a large fraction (28%) of newly replicated DNA molecules. Thus, the DNA in the 26S histone-deficient 40S chromatin cannot replicate without the prior and/or concommitant addition of protein which increases its sedimentation rate to 41-55S. Nevertheless, when compared with normal 55S viral chromatin, the histone-deficient SV40 chromatin had nearly a 3-fold greater probability of functioning as a template for a subsequent round of replication.