Degradation pathway of CopA, the antisense RNA that controls replication of plasmid R1.
RNA decay in bacteria is carried out by a number of enzymes that participate in the coordinated degradation of their substrates. Endo- and exonucleolytic cleavages as well as polyadenylation are generally involved in determining the half-life of RNAs. Small, untranslated antisense RNAs are suitable model systems to study decay. A study of the pathway of degradation of CopA, the copy number regulator RNA of plasmid R1, is reported here. Strains carrying mutations in the genes encoding RNase E, polynucleotide phosphorylase (PNPase), RNase II and poly(A) polymerase I (PcnB/PAP I)--alone or in combination--were used to investigate degradation patterns and relative half-lives of CopA. The results obtained suggest that RNase E initiates CopA decay. Both PNPase and RNase II can degrade the major 3'-cleavage product generated by RNase E. This exonucleolytic degradation is aided by PcnB, which may imply a requirement for A-tailing. RNase II can partially protect CopA's 3'-end from PNPase-dependent degradation. Other RNases are probably involved in decay, since in rnb/pnp double mutants, decay still occurs, albeit at a reduced rate. Experiments using purified RNase E identified cleavage sites in CopA in the vicinity of, but not identical to, those mapped in vivo, suggesting that the cleavage site specificity of this RNase is modulated by additional proteins in the cell. A model of CopA decay is presented and discussed.
Söderbom
Fredrik
F
Department of Microbiology, Biomedical Center, Uppsala UniversityBox 581, S-75123 UppsalaSweden.
Wagner
E Gerhart H
EGH
Department of Microbiology, SLU (Swedish University of Agricultural Sciences)Box 7025, S-75007 UppsalaSweden.
D001426:Bacterial Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D004722:Endoribonucleases / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005095:Exoribonucleases / Q000378:metabolism; D009154:Mutation; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism*; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism; D011117:Polyribonucleotide Nucleotidyltransferase / Q000378:metabolism; D016372:RNA, Antisense / Q000378:metabolism*
D001426:Bacterial Proteins; C071263:CopA protein, Bacteria; D016372:RNA, Antisense; D011062:Polynucleotide Adenylyltransferase; D011117:Polyribonucleotide Nucleotidyltransferase; D004722:Endoribonucleases; D005095:Exoribonucleases; C022535:exoribonuclease II; C022537:ribonuclease E