Identification of a DinB/UmuC homolog in the archeon Sulfolobus solfataricus

To date, eight closely related homologs of the Escherichia coli UmuC protein have been identified. All of these homologs appear to play critical roles in damage-inducible mutagenesis in enterobacteriaceae. Recently, a distantly related UmuC-homolog, DinB, has also been identified in E. coli. Using the polymerase chain reaction together with degenerate primers designed against conserved regions found in UmuC-like proteins, we have identified a new member of the UmuC-superfamily in the archeon Sulfolobus solfataricus. This new homolog shows high sequence similarity to DinB and a lower level of similarity to UmuC. As a consequence, we have called this new gene dbh (dinB homolog). Analysis of approximately 2.7 kb DNA encompassing the dbh region revealed several open reading frames (orfs). One, encoding a putative ribokinase, was located immediately upstream of dbh. This orf overlaps the dbh gene by 4 bp suggesting that both proteins might be coordinately expressed. Further upstream of the ribokinase-dbh locus was another orf encoding a potential ATPase homologous to two uncharacterized S. cerevisiae proteins (YD9346.02c and SC38KCXVI_20) and another E. coli DNA repair protein, RuvB. While this is the first report of a UmuC-like homolog in an archeon, we detected additional homologs using protein sequence comparisons in Gram-positive bacteria, cyanobacteria, and among potential human EST products, indicating that UmuC-related proteins comprise a ubiquitous superfamily of proteins probably involved in DNA repair and mutagenesis.