TY - JOUR
T1 - A putative ubiquitin ligase required for efficient mRNA export differentially affects hnRNP transport
AU - Duncan, Kent
AU - Umen, James G.
AU - Guthrie, Christine
N1 - Funding Information:
We thank Erin O'Shea, Arie Kaffman, Arash Komeili, Nicole Miller Rank, and Karsten Weis for plasmids and helpful discussions; Chris Brandl and Maurice Swanson for strains, antibodies and communicating results prior to publication; John Aris for antibodies; Ed Hurt, Joachim Li and Pam Silver for providing strains and plasmids; Anne de Bruyn Kops, Julianne Dunphy, Wendy Gilbert, Maki Inada, Amy Kistler, Erin O’Shea, Pascal Preker, and Jon Staley for critical reading of the manuscript; Henrike Scholz for much support, discussion, and assistance with the alignments; and Lucita Esperas, Carol Pudlow, and Heli Roiha for superb technical support. This work was supported by a grant from the NIH to C.G. and an NIH training grant. C.G. is an American Cancer Society Research Professor of Molecular Genetics.
PY - 2000/6/1
Y1 - 2000/6/1
N2 - Background: In the nucleus, mRNAs are bound by hnRNP proteins. A subset of hnRNP proteins shuttle between the nucleus and cytoplasm and are believed to promote mRNA export by acting as adaptors between mRNA and the transport machinery. The existence of multiple shuttling hnRNP proteins raises the question of whether differentially regulated, hnRNP-specific mRNA export pathways exist. Results: We have determined that Tom1p, a conserved protein with a hect (homology to E6-AP carboxyl terminus) E3 ubiquitin ligase domain, is required for efficient mRNA export in S. cerevisiae, yet differentially affects hnRNP protein localization and export. Mutations in tom I predicted to abolish ubiquitin ligase activity block efficient export of Nab2p and mRNA, causing Nab2p-mRNA complexes to accumulate in a punctate pattern coincident with the nuclear pore complex (NPC). Notably, the subcellular distribution of several other hnRNP proteins is not affected. In particular, Npl3p remains mRNA-associated and continues to be efficiently exported in tom1 mutants. Conclusion: Our results demonstrate that mutations predicted to affect the enzymatic activity of the Tom1p ubiquitin ligase differentially affect export of hnRNP proteins in association with mRNA. We propose the existence of multiple mRNA export pathways, with export of Nab2p-associated mRNAs dependent on a branch of the ubiquitin protein modification pathway.
AB - Background: In the nucleus, mRNAs are bound by hnRNP proteins. A subset of hnRNP proteins shuttle between the nucleus and cytoplasm and are believed to promote mRNA export by acting as adaptors between mRNA and the transport machinery. The existence of multiple shuttling hnRNP proteins raises the question of whether differentially regulated, hnRNP-specific mRNA export pathways exist. Results: We have determined that Tom1p, a conserved protein with a hect (homology to E6-AP carboxyl terminus) E3 ubiquitin ligase domain, is required for efficient mRNA export in S. cerevisiae, yet differentially affects hnRNP protein localization and export. Mutations in tom I predicted to abolish ubiquitin ligase activity block efficient export of Nab2p and mRNA, causing Nab2p-mRNA complexes to accumulate in a punctate pattern coincident with the nuclear pore complex (NPC). Notably, the subcellular distribution of several other hnRNP proteins is not affected. In particular, Npl3p remains mRNA-associated and continues to be efficiently exported in tom1 mutants. Conclusion: Our results demonstrate that mutations predicted to affect the enzymatic activity of the Tom1p ubiquitin ligase differentially affect export of hnRNP proteins in association with mRNA. We propose the existence of multiple mRNA export pathways, with export of Nab2p-associated mRNAs dependent on a branch of the ubiquitin protein modification pathway.
UR - http://www.scopus.com/inward/record.url?scp=0034659266&partnerID=8YFLogxK
U2 - 10.1016/S0960-9822(00)00527-3
DO - 10.1016/S0960-9822(00)00527-3
M3 - Article
C2 - 10873801
AN - SCOPUS:0034659266
SN - 0960-9822
VL - 10
SP - 687
EP - 696
JO - Current Biology
JF - Current Biology
IS - 12
ER -