Intragenic suppressors of temperature-sensitive rne mutations lead to the dissociation of RNase E activity on mRNA and tRNA substrates in Escherichia coli.
RNase E of Escherichia coli is an essential endoribonuclease that is involved in many aspects of RNA metabolism. Point mutations in the S1 RNA-binding domain of RNase E (rne-1 and rne-3071) lead to temperature-sensitive growth along with defects in 5S rRNA processing, mRNA decay and tRNA maturation. However, it is not clear whether RNase E acts similarly on all kinds of RNA substrates. Here we report the isolation and characterization of three independent intragenic second-site suppressors of the rne-1 and rne-3071 alleles that demonstrate for the first time the dissociation of the in vivo activity of RNase E on mRNA versus tRNA and rRNA substrates. Specifically, tRNA maturation and 9S rRNA processing were restored to wild-type levels in each of the three suppressor mutants (rne-1/172, rne-1/186 and rne-1/187), while mRNA decay and autoregulation of RNase E protein levels remained as defective as in the rne-1 single mutant. Each single amino acid substitution (Gly-->Ala at amino acid 172; Phe --> Cys at amino acid 186 and Arg --> Leu at amino acid 187) mapped within the 5' sensor region of the RNase E protein. Molecular models of RNase E suggest how suppression may occur.
Perwez
Tariq
T
Department of Genetics and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
Hami
Danyal
D
Maples
Valerie F
VF
Min
Zhao
Z
Wang
Bi-Cheng
BC
Kushner
Sidney R
SR
D000483:Alleles; D004722:Endoribonucleases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D005804:Genes, Lethal; D006706:Homeostasis; D009154:Mutation; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D012341:RNA, Ribosomal, 5S / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D013379:Substrate Specificity; D013489:Suppression, Genetic; D013696:Temperature
D012333:RNA, Messenger; D012341:RNA, Ribosomal, 5S; D012343:RNA, Transfer; D004722:Endoribonucleases; C022537:ribonuclease E