Studies on the biological role of DNA methylation: III. Role in excision of one-genome long single-stranded ?X174 DNA

摘要

Accumulation of replicative intermediates of the bacteriophage ?X174 was observed in E.coli C infected cells when phage DNA methylation has been inhibited by nicotinamide or when cells were infected with a temperature-sensitive mutant in gene A. Analysis of the accumulating replicative intermediates by electron microscopy revealed that these molecules are composed of double-stranded DNA rings with multiple-genome length single-stranded “tails”. These results suggest that the single 5-methylcytosine residue present in the phage DNA serves as a recognition site for the gene A protein mediating the excision of one-genome long phage DNA. This excision process is obligatory for the final maturation of the phage.