title: Nuclear retention prevents premature cytoplasmic appearance of mRNA.
abstract: In S. cerevisiae cells debilitated in mRNA nuclear export, transcripts are retained in nuclear foci ("dots"). The ultimate fate of dot-mRNA has remained elusive. Here, we use single molecule counting microscopy and (35)S-methionine pulse-labeling assays to quantify cytoplasmic HSP104 RNA levels and estimate HSP104 RNA translation status. HSP104 transcripts, retained in dots as a consequence of the mex67-5 mutation, are slowly released over time for cytoplasmic translation. Thus, dot-mRNA retains function. However, forcing its nuclear export, by overexpressing the Sub2p mRNA export factor, does not elevate Hsp104p protein levels but is instead paralleled by growth deficiency. Nuclear export and growth phenotypes are both counteracted by coexpressing the nuclear RNA quality control factor Rrp6p. Thus, prematurely released dot-mRNA is translationally inactive and possibly toxic. Accordingly, nuclear retention of mRNA may serve a precautionary role during stressful situations such as, e.g., decreased mRNA maturation competence.
authors.affiliation: Department of Molecular Biology and Genetics, Centre for mRNP Biogenesis and Metabolism, Aarhus University, Aarhus C, Denmark.
authors.forename: Thomas Beuchert
authors.initials: TB
authors.lastname: Kallehauge
authors.forename: Marie-Cécile
authors.initials: MC
authors.lastname: Robert
authors.forename: Edouard
authors.initials: E
authors.lastname: Bertrand
authors.forename: Torben Heick
authors.initials: TH
authors.lastname: Jensen
mesh_terms: D021581:Active Transport, Cell Nucleus; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D006360:Heat-Shock Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; C070972:HsP104 protein, S cerevisiae; D063326:Exosome Multienzyme Ribonuclease Complex; C112610:RRP6 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C027900:RNA-dependent ATPase