Expression of nuclease gene nucA, a member of an operon putatively involved in uracil removal from DNA and its subsequent reuse in Prevotella bryantii.

The genomic region of Prevotella bryantii TC1-1 that conferred an increased nucleolytic activity on Escherichia coli was characterized. It contains two divergent transcriptional units separated by an AT-rich promoter region. One unit is comprised of three genes involved in nucleotide metabolism. nucA, the first gene of this unit, whose product belongs to exonuclease/endonuclease/phosphatase Pfam family, was thought to be required for the increased nucleolytic activity and various expression strategies were employed to confirm its role. The nucA expression was only successful in cell free system where DNase and RNase activity was observed. Two genes downstream of nucA code for a putative uracil DNA glycosylase and uridine kinase which could be involved in the removal of misincorporated uracil from DNA and its reuse. Given that apurinic/apyrimidinic nuclease activity is required after uracil removal from DNA, it was somewhat surprising to find out that nucA, whose product belongs to protein family consisting mostly of apurinic/apyrimidinic nucleases, has no apurinic/apyrimidinic activity.