FIG. 4.

The rate of deadenylation is increased when translation initiation is impaired. Polyacrylamide Northern gels of transcriptional repression experiments examining the deadenylation of PGK1 and accumulation of oligoadenylated mRNAs in various translation initiation mutants are shown. Minutes following transcription repression are given directly above each sample. The top fragment was produced by cleavage of the full-length mRNA with RNase H and oligonucleotide oRP70 (5′-CGGATAAGAAAGCAACACCTGG-3′). This cleavage shortens the mRNA enough to visualize small differences at the 3′ end. The bottom fragment is the decay intermediate stabilized by the poly(G) insertion in the 3′ UTR. The arrow indicates the size of the oligoadenylated mRNA. The numbers after the A’s in the cartoons represent the range of poly(A) tail sizes found on each mRNA species as determined by comparison with the oligo(dT) lanes, in which the poly(A) tails have been completely removed by cleavage with RNase H, oligonucleotide oRP70, and oligo(dT). The blots were probed with oRP141. ts, temperature sensitive.