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Nuclear Rna Surveillance In Saccharomyces Cerevisiae: Trf4p-Dependent Polyadenylation Of Nascent Hypomethylated Trna And An Aberrant Form Of 5s Rrna, Sujatha A. Kadaba, Xuying Wang, James T. Anderson

Biological Sciences Faculty Research and Publications

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 (tRNA_i^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 tRNA_i^Met in vivo. DNA sequence analysis of tRNA_i^Met cDNAs and Northern hybridizations of poly(A)+ RNA provide evidence that nascent pre-tRNA_i^Met transcripts are targeted for polyadenylation and degradation. We determined …