Endonuclease-sensitive regions in SV40 chromatin from cells infected with duplicated mutants

Abstract

Genetic information required for the presence of an endonuclease-sensitive region in SV40 chromatin has been investigated by use of viral mutants duplicated for some or all of the sequences which are nuclease sensitive in wild-type SV40 chromatin. Nuclear extracts were prepared from mutant-infected BSC-1 cells, endogenous nuclease present in the nuclear extract was allowed to introduce double-strand cuts into viral chromatin, and the distribution of preferential cutting sites was determined by restriction enzyme mapping. ev-1114, ev-1119, in(Or)-1412, and mutant 1415 exhibited nuclease-sensitive regions corresponding to each duplicated segment. Hence, it is likely that the genome segment between map positions 0.65 and 0.69 provides sufficient cis-information to organize the nuclease-sensitive chromatin configuration. A functional origin for viral replication is not required. The duplicated segments of ev-1114 differ substantially in their susceptibility to cleavage by endogenous endonuclease and BglI. From this it is concluded that genetic information between map positions 0.71 and 0.75 contributes substantially to the degree of accessibility throughout the nuclease-sensitive region.