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PMID: 15037768 Published · ppublish English Journal Article Research Support, U.S. Gov't, P.H.S.

Transportins 1 and 2 are redundant nuclear import factors for hnRNP A1 and HuR.

RNA (New York, N.Y.) ·Vol. 10 ·No. 4 ·2004-04-00 ·Pages 590-9

Rebane A, Aab A, Steitz JA

Abstract

Several mRNA-binding proteins, including hnRNP A1 and HuR, contain bidirectional transport signals that mediate both their nuclear import and export. Previously, Transportin 1 (Trn1) was identified as a mediator of hnRNP A1 import, whereas the closely related protein Transportin 2 (Trn2) was shown to interact with HuR. Here we have investigated the subfamily of transportins that consists of Trn1 (or Kap beta2A) and two alternatively spliced Trn2 isoforms (Trn2a and Trn2b), also called Trn2 and Kap beta2B. The sequence differences among these proteins could alter either their cargo specificity or their response to RanGTP and thus their function as import or export receptors. Using in vitro binding assays, we show that hnRNP A1 preferentially binds Trn1 and Trn2b versus Trn2a. HuR interacts with all three transportins, as well as weakly with Imp beta. The hnRNP A1 and HuR shuttling domains, called M9 and HNS, respectively, are sufficient for these interactions. Despite small differences in the binding of HuR and hnRNP A1 to the three transportins, in vitro interaction studies performed in the presence and absence of RanQ69LGTP indicate that all three transportins most likely act as import factors for HuR and hnRNP A1. In digitonin-permeabilized HeLa cells, both M9 and HNS peptides compete for the import of recombinant hnRNP A1 and HuR, indicating that HuR and hnRNP A1 import pathways are at least partially overlapping. Possible nucleocytoplasmic shuttling mechanisms for hnRNP A1 and HuR are discussed.

MeSH Terms
Active Transport, Cell Nucleus/physiology Amino Acid Sequence Antigens, Surface/metabolism Cell Nucleus/metabolism ELAV Proteins ELAV-Like Protein 1 HeLa Cells Heterogeneous Nuclear Ribonucleoprotein A1 Heterogeneous-Nuclear Ribonucleoprotein Group A-B/metabolism Humans Molecular Sequence Data Mutation Protein Structure, Tertiary RNA-Binding Proteins/metabolism Receptors, Cytoplasmic and Nuclear/metabolism Sequence Analysis, Protein beta Karyopherins/metabolism ran GTP-Binding Protein/genetics,metabolism
Chemicals
Antigens, Surface ELAV Proteins ELAV-Like Protein 1 ELAVL1 protein, human Heterogeneous Nuclear Ribonucleoprotein A1 Heterogeneous-Nuclear Ribonucleoprotein Group A-B RNA-Binding Proteins Receptors, Cytoplasmic and Nuclear TNPO1 protein, human TNPO2 protein, human beta Karyopherins ran GTP-Binding Protein
Authors & Affiliations
3 authors, click to expand affiliations / ORCID
Rebane Ana
Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Aab Alar
Steitz Joan A
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Article Info
Journal
RNA (New York, N.Y.)
Abbr.
RNA
ISSN
1355-8382
DOI
10.1261/rna.5224304
Published
2004-04-00
Pages
590-9
Language
English
Region
United States
NLM ID
9509184
PMCID
PMC1370549
Subset
IM
Grants
NCI NIH HHS · P01 CA016038 · United States
NCI NIH HHS · CA 16038 · United States
External Links
PubMed source DOI: 10.1261/rna.5224304 PMC Full Text View journal details
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