Interaction between Ski7p and Upf1p is required for nonsense-mediated 3'-to-5' mRNA decay in yeast.
Aberrant mRNAs containing premature termination codons (PTC-mRNAs) are degraded by a conserved surveillance system, referred to as the nonsense- mediated decay (NMD) pathway. Although NMD is reported to operate on the decapping and 5'-to-3' exonucleolytic decay of PTC-mRNAs without affecting deadenylation, a role for an opposite 3'-to-5' decay pathway remains largely unexplored. In this study, we have characterized the 3'-to-5' directed mRNA degradation in the yeast NMD pathway. PTC-mRNAs are stabilized in yeast cells lacking the components of 3'-to-5' mRNA-decay machinery. The 3'-to-5' directed degradation of PTC-mRNAs proceeds more rapidly than that of the PTC-free transcript, in a manner dependent on the cytoplasmic exosome and Upf proteins. Moreover, Upf1p, but not Upf2p, interacts physically with an N-terminal domain of Ski7p, although the interaction requires Upf2p. The efficiency of 3'-to-5' directed degradation of PTC-mRNAs is impaired by overexpression of Ski7p N-domain fragments that contain a sequence of the Upf1p-interaction region. These data suggest that the activation of 3'-to-5' directed NMD is mediated through the interaction between Upf1p and the Ski7p N domain.
Takahashi
Shinya
S
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.
Araki
Yasuhiro
Y
Sakuno
Takeshi
T
Katada
Toshiaki
T
D048868:Adaptor Proteins, Signal Transducing; D001483:Base Sequence; D003593:Cytoplasm / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011233:Precipitin Tests; D011485:Protein Binding; D020365:RNA Helicases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; C118668:SKI7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases