SPATIAL CONSEQUENCES OF DEFECTIVE PROCESSING OF SPECIFIC YEAST MESSENGER-RNAS REVEALED BY FLUORESCENT IN-SITU HYBRIDIZATION

This work introduces the first use of fluorescent in situ hybridizatio n (FISH) to detect the distribution of specific transcripts in Sacchar omyces cerevisiae. We have applied this technique to analysis of repor ter transcripts from a single, integrated copy, or multicopy plasmids. We have evaluated the effect of splice site deletions or the presence or absence of a terminator/cleavage site and demonstrated that both s plicing and polyadenylation affect the export of these transcripts fro m the nucleus to the cytoplasm. Moreover, we show that the exported pr e-mRNAs are substrates for nonsense codon-mediated decay through the U PF1 pathway. The work presented here demonstrates that the spatial dis tribution of transcripts will also be an important component of yeast RNA metabolism.