title: Nonsense-mediated decay does not occur within the yeast nucleus.
abstract: Nonsense-mediated decay (NMD) is a eukaryotic regulatory process that degrades mRNAs with premature termination codons (PTCs). Although NMD is a translation-dependent process, there is evidence from mammalian systems that PTC recognition and mRNA degradation takes place in association with nuclei. Consistent with this notion, degradation of mammalian PTC-containing mRNAs occurs when they are bound by the cap binding complex (CBC) during a "pioneer" round of translation. Moreover, there are reports indicating that a PTC can trigger other nuclear events such as alternative splicing, abnormal 3' end processing, and accumulation of pre-mRNA at transcription sites. To examine whether a PTC can elicit similar nuclear events in yeast, we used RNA export-defective mutants to sequester mRNAs within nuclei. The results indicate that nuclear PTC-containing yeast RNAs are NMD insensitive. We also observed by fluorescent in situ hybridization that there was no PTC effect on mRNA accumulated at the site of transcription. Finally, we show that yeast NMD occurs minimally if at all on CBC-bound transcripts, arguing against a CBC-mediated pioneer round of translation in yeast. The data taken together indicate that there are no direct consequences of a PTC within the yeast nucleus.
authors.affiliation: Howard Hughes Medical Institute, Department of Biology, Brandeis University, 415 South St., Waltham, MA 02454, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Kuperwasser
authors.forename: Saverio
authors.initials: S
authors.lastname: Brogna
authors.forename: Ken
authors.initials: K
authors.lastname: Dower
authors.forename: Michael
authors.initials: M
authors.lastname: Rosbash
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D018389:Codon, Nonsense / Q000235:genetics* / Q000378:metabolism*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D017404:In Situ Hybridization, Fluorescence; D039381:RNA Cap-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012331:RNA, Fungal / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018389:Codon, Nonsense; D039381:RNA Cap-Binding Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins