Nuclear RNA surveillance in Saccharomyces cerevisiae: Trf4p-dependent polyadenylation of nascent hypomethylated tRNA and an aberrant form of 5S rRNA.
1-Methyladenosine modification at position 58 of tRNA is catalyzed by a two-subunit methyltransferase composed of Trm6p and Trm61p in Saccharomyces cerevisiae. Initiator tRNA (tRNAi(Met)) lacking m1A58 (hypomethylated) is rendered unstable through the cooperative function of the poly(A) polymerases, Trf4p/Trf5p, and the nuclear exosome. We provide evidence that a catalytically active Trf4p poly(A) polymerase is required for polyadenylation of hypomethylated tRNAi(Met) in vivo. DNA sequence analysis of tRNAi(Met) cDNAs and Northern hybridizations of poly(A)+ RNA provide evidence that nascent pre-tRNAi(Met) transcripts are targeted for polyadenylation and degradation. We determined that a mutant U6 snRNA and an aberrant form of 5S rRNA are stabilized in the absence of Trf4p, supporting that Trf4p facilitated RNA surveillance is a global process that stretches beyond hypomethylated tRNAi(Met). We conclude that an array of RNA polymerase III transcripts are targeted for Trf4p/ Trf5p-dependent polyadenylation and turnover to eliminate mutant and variant forms of normally stable RNAs.
Kadaba
Sujatha
S
Department of Biological Sciences, Marquette University, P.O. Box 1881, Wehr Life Sciences, Milwaukee, WI 53201, USA.
Wang
Xuying
X
Anderson
James T
JT
D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D016297:Mutagenesis, Site-Directed; D012322:RNA Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012341:RNA, Ribosomal, 5S / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D004271:DNA, Fungal; D012322:RNA Precursors; D012331:RNA, Fungal; D012341:RNA, Ribosomal, 5S; D012342:RNA, Small Nuclear; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins; C405486:U6 small nuclear RNA; C045783:pre-tRNA(Met); D012343:RNA, Transfer; D012321:DNA-Directed RNA Polymerases; C506067:Trf5 protein, S cerevisiae; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae