RNase T affects Escherichia coli growth and recovery from metabolic stress.
To determine the essentiality and role of RNase T in RNA metabolism, we constructed an Escherichia coli chromosomal rnt::kan mutation by using gene replacement with a disrupted, plasmid-borne copy of the rnt gene. Cell extracts of a strain with mutations in RNases BN, D, II, and I and an interuppted rnt gene were devoid of RNase T activity, although they retained a low level (less than 10%) of exonucleolytic activity on tRNA-C-C-[14C]A due to two other unidentified RNases. A mutant lacking tRNA nucleotidyltransferase in addition to the aforementioned RNases accumulated only about 5% as much defective tRNA as did RNase T-positive cells, indicating that this RNase is responsible for essentially all tRNA end turnover in E. coli. tRNA from rnt::kan strains displayed a slightly reduced capacity to be aminoacylated, raising the possibility that RNase T may also participate in tRNA processing. Strains devoid of RNase T displayed slower growth rates than did the wild type, and this phenotype was accentuated by the absence of the other exoribonucleases. A strain lacking RNase T and other RNases displayed a normal response to UV irradiation and to the growth of bacteriophages but was severely affected in its ability to recover from a starvation regimen. The data demonstrate that the absence of RNase T affects the normal functioning of E. coli, but it can be compensated for to some degree by the presence of other RNases. Possible roles of RNase T in RNA metabolism are discussed.
Padmanabha
K P
KP
Department of Biochemistry, University of Connecticut Health Center, Farmington 06432.
Deutscher
M P
MP
D015139:Blotting, Southern; D002455:Cell Division / Q000502:physiology*; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D005095:Exoribonucleases / Q000502:physiology*; D015870:Gene Expression; D066298:In Vitro Techniques; D010957:Plasmids; D012313:RNA / Q000378:metabolism*; D015183:Restriction Mapping; D014170:Transformation, Genetic
D012313:RNA; D004247:DNA; D005095:Exoribonucleases; C042081:exoribonuclease T