Lack of GATC sites in the genome of Streptococcus bovis bacteriophage F4

A strong bias against GATC sites was observed in the genome of phage F4, a lytic Streptococcus bovis bacteriophage. Only three GATC sites were found w ithin the 60.4-kbp genome of this phage. The comparative lack of GATC seque nces within the F4 genome was probably not due to dam methylation, as no mo dification within this site was detected using methylation-sensitive isosch izomer pair restriction endonuclease analysis. The short oligonucleotide co mposition of available S. bovis DNA sequences suggested the existence of an unknown mechanism for counterselection of GATC sites in S. bovis bacteriop hages. (C) 2000 Editions scientifiques et medicales Elsevier SAS.