FIG. 6.

Effects of single or mutiple deletions of UPF1, NMD2, UPF3, and XRN1 on the accumulation of capped and decapped wild-type mRNAs. (A and B) Analysis of the levels of capped and decapped wild-type (WT) mRNAs by anti-m⁷ G immunoprecipitation. Total RNA was isolated from yeast strains of the indicated genotypes, and anticap immunoprecipitation was carried out as in Fig. 1B. DNA probes specific for URA5, TCM1, and PGK1 were used for Northern analysis of the respective RNA fractions. Lanes I, S, and P represent input, supernant, and pellet, respectively. Quantitation of this experiment is summarized in Table 3. (C) Analysis of the levels of URA5 mRNA decay intermediates. Primer extension analysis of the URA5 mRNA was performed on total RNA from each indicated yeast strain, as in Fig. 3A. Total RNA isolated from the upf3Δ strain was used as a control. The major transcriptional start sites of the URA5 mRNA and the 5′ ends of its decay intermediates are indicated by arrows and asterisks, respectively.