RNase E and polyadenyl polymerase I are involved in maturation of CI RNA, the P4 phage immunity factor.
Bacteriophage P4 immunity is controlled by a small stable RNA (CI RNA) that derives from the processing of primary transcripts. In previous works, we observed that the endonuclease RNase P is required for the maturation of CI RNA 5'-end; moreover, we found that polynucleotide phosphorylase (PNPase), a 3' to 5' RNA-degrading enzyme, is required for efficient 5'-end processing of CI RNA, suggesting that 3'-end degradation of the primary transcript might be involved in the production of proper RNase P substrates. Here, we demonstrate that another Escherichia coli nuclease, RNase E, would appear to be involved in this process. We found that transcripts of the P4 immunity region are modified by the post-transcriptional addition of short poly(A) tails and heteropolymeric tails with prevalence of A residues. Most oligoadenylated transcripts encompass the whole cI locus and are thus compatible as intermediates in the CI RNA maturation pathway. On the contrary, in a polynucleotide phosphorylase (PNPase)-defective host, adenylation occurred most frequently within cI, implying that such transcripts are targeted for degradation. We did not find polyadenylation in a pcnB mutant, suggesting that the pcnB-encoded polyadenyl polymerase I (PAP I) is the only enzyme responsible for modification of P4 immunity transcripts. Maturation of CI RNA 5'-end in such a mutant was impaired, further supporting the idea that processing of the 3'-end of primary transcripts is an important step for efficient maturation of CI RNA by RNase P.
Briani
Federica
F
Dipartimento di Genetica e di Biologia dei Microrganismi, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy.
Del Vecchio
Emanuela
E
Migliorini
Domenico
D
Hajnsdorf
Eliane
E
Régnier
Philippe
P
Ghisotti
Daniela
D
Dehò
Gianni
G
D001483:Base Sequence; D003090:Coliphages / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*
D012333:RNA, Messenger; D012367:RNA, Viral; D011062:Polynucleotide Adenylyltransferase; D004722:Endoribonucleases; C022537:ribonuclease E