Sequence of the bacteriophage SP01 gene coding for transcription factor 1, a viral homologue of the bacterial type II DNA-binding proteins.

The Bacillus subtilis phage SP01, whose DNA contains 5-hydroxymethyluracil (hmUra) in place of thymine, codes for an abundant, small, basic protein called TF1. TF1 binds preferentially to hydroxymethyluracil-containing DNA and thereby selectively inhibits transcription of such DNA in vitro. The gene for TF1 has been sequenced. We find that this viral protein is a homologue of the ubiquitous bacterial type II DNA-binding proteins. The three-dimensional structure of one of these bacterial proteins has recently been determined. We are able to discern common as well as distinctive features in the amino acid sequence and the three-dimensional structure of the homologous viral protein.