Identification of a potent DNase activity associated with RNase T of Escherichia coli.
RNase T was first identified as an enzyme responsible for end turnover of tRNA in Escherichia coli. Its activity, specific for tRNA-C-C-A, catalyzes the release of tRNA-C-C and AMP. RNase T, along with several other RNases, plays a role in maturation of several other RNA species by a similar limited nuclease activity. In previous work, we identified the gene for RNase T, rnt, as a high copy suppressor of the UV sensitivity conferred by deficiency in three single-strand DNA-specific exonucleases, RecJ, exonuclease I, and exonuclease VII. This suggested that RNase T may process DNA substrates as well. In this work, we show that purified RNase T possesses a potent 3' to 5' single-strand DNA-specific exonucleolytic activity. Its Km for single-strand DNA substrates is many orders of magnitude lower than that for tRNA, suggesting that single-strand DNA may be a natural biological substrate for RNase T. We suggest that the DNase activity of RNase T may play a role in end trimming reactions during DNA recombination and/or DNA repair.
Viswanathan
M
M
Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
Dower
K W
KW
Lovett
S T
ST
D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D005090:Exodeoxyribonucleases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D011994:Recombinant Proteins; D005090:Exodeoxyribonucleases; D005095:Exoribonucleases; C042081:exoribonuclease T; D008274:Magnesium