Figure 2. 3′ RNA fragments are decay intermediates dependent on XRN1 activity and translation.

(a,b) Northern blot analysis of PTC-containing PGK1 reporter mRNA in upf1Δ cells expressing ATPase-deficient UPF1 in the presence (UPF1-DE) or absence of XRN1 (UPF1-DE/xrn1Δ). (b) Reporter mRNA inhibited for translation by a 5′ stemloop in upf1Δ cells expressing either wild-type (WT) or ATPase-deficient (DE) UPF1. Full-length reporter mRNA (FL) and 3′ RNA fragments (arrow) indicated. RNA levels were normalized to NMD-insensitive SCR1 RNA. Results are representative of three independent experiments. Nt, nucleotide.