Nuclear RNA surveillance in Saccharomyces cerevisiae: Trf4p-dependent polyadenylation of nascent hypomethylated tRNA and an aberrant form of 5S rRNA

Internally truncated U6 snRNA is a substrate for Trf4p polyadenylation and degradation by the nuclear exosome. Wild type (F39), rrp6Δ (F23), trf4Δ (F22), and trf4Δ + Sctrf4-236 were transformed with a single-copy number plasmid containing a mutant SNR6 gene (snr6Δ59–72). Total RNA (5 μg) from single transformants and a wildtype strain bearing an empty plasmid were analyzed by Northern hybridization using a radiolabeled probe (JA242) that recognizes the endogenous and plasmid-borne U6 snRNAs. The migration positions of the endogenous and snr6Δ59–72 mutant U6 snRNAs are shown for clarity.