Regulation of NAB2 mRNA 3'-end formation requires the core exosome and the Trf4p component of the TRAMP complex.
The nuclear exosome functions in a variety of pathways catalyzing formation of mature RNA 3'-ends or the destruction of aberrant RNA transcripts. The RNA 3'-end formation activity of the exosome appeared restricted to small noncoding RNAs. However, the nuclear exosome controls the level of the mRNA encoding the poly(A)-binding protein Nab2p in a manner requiring an A(26) sequence in the mRNA 3' untranslated regions (UTR), and the activities of Nab2p and the exosome-associated exoribonuclease Rrp6p. Here we show that the A(26) sequence inhibits normal 3'-end processing of NAB2 mRNA in vivo and in vitro, and makes formation of the mature 3'-end dependent on trimming of the transcript by the core exosome and the Trf4p component of the TRAMP complex from a downstream site. The detection of mature, polyadenylated transcripts ending at, or within, the A(26) sequence indicates that exosome trimming sometimes gives way to polyadenylation of the mRNA. Alternatively, Rrp6p and the TRAMP-associated Mtr4p degrade these transcripts thereby limiting the amount of Nab2p in the cell. These findings suggest that NAB2 mRNA 3'-end formation requires the exosome and TRAMP complex, and that competition between polyadenylation and Rrp6p-dependent degradation controls the level of this mRNA.
Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA.
Kelly M
KM
Roth
Joel
J
Byam
Feng
F
Fang
J Scott
JS
Butler
D020413:3' Untranslated Regions / Q000378:metabolism; D001483:Base Sequence; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics* / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000235:genetics / Q000378:metabolism; D026723:Polyadenylation; D026721:RNA 3' End Processing; D020871:RNA Stability; D012331:RNA, Fungal / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*
D020413:3' Untranslated Regions; C080773:NAB2 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D039102:Poly(A)-Binding Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; D005095:Exoribonucleases