Effects of 5′ and 3′ deletions of the YRA1 intron on Edc3p-mediated YRA1 pre-mRNA decay.

A set of yra1 alleles containing 3′ or 5′ deletions of the YRA1 intron was constructed and the steady-state levels of transcripts encoded by each of these alleles in wild-type (1), upf1Δ (2), edc3Δ (3), and upf1Δedc3Δ (4) cells were determined by Northern blotting. Blots were hybridized with probes complementary to the YRA1 or SCR1 transcripts, with the latter serving as a loading control. The positions of YRA1 pre-mRNAs encoded by the endogenous and all the exogenous YRA1 alleles are marked by a triangle and by diamonds, respectively. A schematic diagram of the yra1 alleles analyzed is shown above the Northern blot, with the relative position of each deletion indicated. Pre-mRNAs encoded by each of the YRA1 mutant alleles cannot be spliced to produce mRNAs, as the 5′ or 3′ splicing signals were deleted from these pre-mRNAs.