Nucleotide sequence of the J gene and surrounding untranslated regions of phage G4 DNA: comparison with phage phiX174.

A 290 nucleotide long region of the bacteriophage G4 genome including the end of the overlapping genes D and E, the entire gene J and the untranslated region between genes J and F has been sequenced and compared with the same region in bacteriophage phiX174. Deletions, insertions, duplications and single base changes in G4 relative to phiX174 have resulted in the following changes: the loss of the phiX174 overlapping gene Dtermination and gene J initiation codons, resulting in their separation by 32 untranslated nucleotides; the deletion of one third of the gene J coding region, so that the G4 protein is only 24 amino acids long compared with 37 amino acids in phiX174; and the establishment of a long untranslated region between G4 genes J and F, which despite many nucleotide changes retains the ability to form a stable hairpin loop in the same place and with the same geometry as in phiX174. The G4 overlapping gene E is longer than in phiX174 and extends beyond gene D. Sixteen nucleotides at the end of genes D and E in phiX174 are duplicated in G4 before gene J.