An E. coli DNA fragment 118 base pairs in length provides dnaY+ complementing activity.

The dnaY gene of E. coli, thought to be involved in the polymerization phase of DNA replication, was localized on a fragment 118 base pairs in length. This fragment, cloned in two different vectors and tested in a dnaY (Ts) recA host, has dnaY + complementing activity. The nucleotide sequence of the 118 base pairs and flanking bases was determined. The dnaY complementing activity was inactivated by transposon insertion and by localized chemical mutagenesis. Three independent insertions of Tn5 into the 118 base pair region eliminated dnaY activity. Eight single-base-change mutations that resulted in loss of dnaY activity also were located within the 118 base pair region. Analysis of the nucleotide sequence reveals a potential promoter but reveals no open reading frames likely to be translated into polypeptides. However, an RNA transcript of the dnaY region is synthesized in vivo. Perhaps the active product of dnaY is a small RNA or perhaps the dnaY region functions as a site.