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Mol. Cell. Biol., 03 1997, 1580-1594, Vol 17, No. 3
F He, AH Brown and A Jacobson
Rapid turnover of nonsense-containing mRNAs in Saccharomyces cerevisiae is
dependent on Upf1p, Nmd2p, and Upf3p, the products of the UPF1, NMD2/UPF2,
and UPF3 genes, respectively. We showed previously that Upf1p and Nmd2p
interact and that this interaction is required for nonsense-mediated mRNA
decay (F. He and A. Jacobson, Genes Dev. 9:437- 454, 1995; F. He, A. H.
Brown, and A. Jacobson, RNA 2:153-170, 1996). In this study we have used
the yeast two-hybrid system to define other protein-protein interactions
among the essential components of this decay pathway. Nmd2p-Upf3p and
Upf1p-Upf3p interactions were identified, and the respective domains
involved in these interactions were delineated by deletion analysis. The
domains of Upf1p and Upf3p putatively involved in their mutual interaction
were found to correspond to the domains on the two proteins which interact
with Nmd2p, suggesting that Nmd2p bridges Upf1p and Upf3p. This conclusion
was reinforced by experiments showing that: (i) deletion of NMD2 completely
abolishes interactions between Upf1p and Upf3p and (ii) overexpression of
full-length Nmd2p or Nmd2p fragments that retain Upf1p- and
Upf3p-interacting domains promotes 10- to 200-fold enhancement of
Upf1p-Nmd2p-Upf3p complex formation. These results; the observation that
cells harboring either single or multiple deletions of UPF1, NMD2, and UPF3
inhibit nonsense-mediated mRNA decay to the same extent; and an analysis of
the possible targets of a dominant-negative NMD2 allele indicate that
Upf1p, Nmd2p, Upf3p, and at least one other factor are functionally
dependent, interacting components of the yeast nonsense-mediated mRNA decay
pathway.
Copyright © 1997, American Society for Microbiology
Upf1p, Nmd2p, and Upf3p are interacting components of the yeast nonsense-mediated mRNA decay pathway
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655-0122, USA.
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