title: 5-fluorouracil enhances exosome-dependent accumulation of polyadenylated rRNAs.
abstract: The antimetabolite 5-fluorouracil (5FU) is a widely used chemotherapeutic for the treatment of solid tumors. Although 5FU slows DNA synthesis by inhibiting the ability of thymidylate synthetase to produce dTMP, the drug also has significant effects on RNA metabolism. Recent genome-wide assays for 5FU-induced haploinsufficiency in Saccharomyces cerevisiae identified genes encoding components of the RNA processing exosome as potential targets of the drug. In this report, we used DNA microarrays to analyze the effect of 5FU on the yeast transcriptome and found that the drug causes the accumulation of polyadenylated fragments of the 27S rRNA precursor and that defects in the nuclear exoribonuclease Rrp6p enhance this effect. The size distribution of these RNAs and their sensitivity to Rrp6p suggest that they are normally degraded by the nuclear exosome and a 5'-3' exoribonuclease. Consistent with this hypothesis, 5FU inhibits the growth of RRP6 mutants with defects in the degradation function of the enzyme and it interferes with the degradation of an rRNA precursor. The detection of poly(A)(+) pre-RNAs in strains defective in various steps in ribosome biogenesis suggests that the production of poly(A)(+) pre-rRNAs may be a general result of defects in rRNA processing. These findings suggest that 5FU inhibits an exosome-dependent surveillance pathway that degrades polyadenylated precursor rRNAs.
authors.affiliation: Department of Microbiology and Immunology, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Fang
authors.forename: Jason
authors.initials: J
authors.lastname: Hoskins
authors.forename: J Scott
authors.initials: JS
authors.lastname: Butler
mesh_terms: D000963:Antimetabolites / Q000494:pharmacology*; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex; D005472:Fluorouracil / Q000494:pharmacology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005800:Genes, Fungal; D020411:Oligonucleotide Array Sequence Analysis; D011061:Poly A / Q000235:genetics / Q000378:metabolism*; D026723:Polyadenylation; D012322:RNA Precursors / Q000378:metabolism; D012331:RNA, Fungal / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D005656:Fungal Proteins; D012322:RNA Precursors; D012331:RNA, Fungal; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D029701:Saccharomyces cerevisiae Proteins; D011061:Poly A; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C112610:RRP6 protein, S cerevisiae; D005472:Fluorouracil