IDENTIFICATION OF A DINB /UMUC HOMOLOG IN THE ARCHEON SULFOLOBUS-SOLFATARICUS/

To date, eight closely related homologs of the Escherichia coli UmuC p rotein have been identified. All of these homologs appear to play crit ical roles in damage-inducible mutagenesis in enterobacteriaceae. Rece ntly, a distantly related UmuC-homolog, DinB, has also been identified in E. coli. Using the polymerase chain reaction together with degener ate primers designed against conserved regions found in UmuC like prot eins, we have identified a new member of the UmuC-superfamily in the a rcheon Sulfolobus solfataricus. This new homolog shows high sequence s imilarity to DinB and a lower level of similarity to UmuC. As a conseq uence, we have called this new gene dbh (dinB homolog). Analysis of ap proximately 2.7 kb DNA encompassing the dbh region revealed several op en reading frames (orfs). One, encoding a putative ribokinase, was loc ated immediately upstream of dbh. This olf overlaps the dbh gene by 4 bp suggesting that both proteins might be coordinately expressed. Furt her upstream of the ribokinase-dbh locus was another orf encoding a po tential ATPase homologous to two uncharacterized S. cerevisiae protein s (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 ar cheon, we detected additional homologs using protein sequence comparis ons in Gram-positive bacteria, cyanobacteria, and among potential huma n EST products, indicating that UmuC-related proteins comprise a ubiqu itous superfamily of proteins probably involved in DNA repair and muta genesis.