Deciphering the cellular pathway for transport of poly(A)-binding protein II

Poly(A)-binding protein II (PABP2) is an abundant nuclear protein that binds with high affinity to nascent poly(A) tails, stimulating their extension and controlling their length. In the cytoplasm, a distinct protein (PABP1) binds to poly(A) tails and participates in mRNA translation and stability....

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Bibliographic Details
Published in:RNA (Cambridge) 2000-02, Vol.6 (2), p.245-256, Article S1355838200991908
Main Authors: CALADO, ANGELO, KUTAY, ULRIKE, KÜHN, UWE, WAHLE, ELMAR, CARMO-FONSECA, MARIA
Format: Article
Language:English
Subjects:
3T3 Cells
Amino Acid Sequence
Animals
Base Sequence
Binding Sites - genetics
Biological Transport, Active
Cell Nucleus - metabolism
Cytoplasm - metabolism
DNA Primers - genetics
Green Fluorescent Proteins
HeLa Cells
Humans
Karyopherins
Luciferases - genetics
Luminescent Proteins - genetics
Mice
Microscopy, Fluorescence
Molecular Sequence Data
mRNA transport
Nuclear Proteins - metabolism
poly(A)-binding protein II
Poly(A)-Binding Proteins
Receptors, Cytoplasmic and Nuclear - metabolism
Recombinant Fusion Proteins - chemistry
Recombinant Fusion Proteins - genetics
Recombinant Fusion Proteins - metabolism
RNA, Messenger - metabolism
RNA-Binding Proteins - chemistry
RNA-Binding Proteins - genetics
RNA-Binding Proteins - metabolism
Transfection
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Description
Summary:Poly(A)-binding protein II (PABP2) is an abundant nuclear protein that binds with high affinity to nascent poly(A) tails, stimulating their extension and controlling their length. In the cytoplasm, a distinct protein (PABP1) binds to poly(A) tails and participates in mRNA translation and stability. How cytoplasmic PABP1 substitutes for nuclear PABP2 is still unknown. Here we report that PABP2 shuttles back and forth between nucleus and cytoplasm by a carrier-mediated mechanism. A potential novel type of nuclear localization signal exists at the C-terminus of the protein, a domain that is highly enriched in methylated arginines. PABP2 binds directly to transportin in a RanGTP-sensitive manner, suggesting an involvement of this transport receptor in mediating import of the protein into the nucleus. Although PABP2 is small enough to diffuse passively through the nuclear pores, protein fusion experiments reveal the existence of a facilitated export pathway. Accordingly, no transport of PABP2 to the cytoplasm occurs at 4 °C. In contrast, export of PABP2 continues in the absence of transcription, indicating that transport to the cytoplasm is independent of mRNA traffic. Thus, rather than leaving the nucleus as a passive passenger of mRNAs, the data suggest that PABP2 interacts with the nuclear export machinery and may therefore contribute to mRNA transport.
ISSN:1355-8382
1469-9001
DOI:10.1017/S1355838200991908