A nuclear matrix-associated factor, SAF-B, interacts with specific isoforms of AUF1/hnRNP D.

One class of heterogeneous nuclear ribonucleoproteins (hnRNPs), AUF1/hnRNP D, consists of four isoform proteins (p45, p42, p40, and p37) which are generated by alternative splicing. The present study was therefore undertaken to clarify any isoform-specific differences in terms of their functions and nucleocytoplasmic localization. All isoforms primarily localized in the ...
nucleus. However, heterokaryon analysis and a study using RNA polymerase II inhibitor revealed that p40/p37 exhibited a continuous shuttling between the nucleus and cytoplasm. Constant nuclear retention activity was mapped to the p45/p42-specific sequence at the C-terminal region, which is retained by alternative splicing. Using this domain as a probe, we performed a yeast two-hybrid screening and we found that scaffold attachment factor B (SAF-B), a nuclear matrix-associated protein, exhibits protein-protein interaction to this region. Colocalization of p45/p42 and SAF-B was observed as a speckle in the nucleus. Interestingly, p45/p42 isoforms appeared to act as a negative regulator in gene expression by forming a complex with SAF-B. Thus, the present study revealed that the isoform-specific functions of AUF1/hnRNP D are defined by intracellular shuttling capacity.
Mesh Terms:
3T3 Cells, Animals, Base Sequence, Biological Transport, Active, Cell Nucleus, Cytoplasm, DNA Primers, DNA-Binding Proteins, Gene Expression, Hela Cells, Heterogeneous-Nuclear Ribonucleoprotein D, Heterogeneous-Nuclear Ribonucleoproteins, Humans, Matrix Attachment Region Binding Proteins, Mice, Nuclear Matrix, Nuclear Matrix-Associated Proteins, Nuclear Proteins, Protein Isoforms, RNA-Binding Proteins, Receptors, Estrogen, Recombinant Fusion Proteins, Ribonucleoproteins, Two-Hybrid System Techniques
Arch. Biochem. Biophys.
Date: Aug. 15, 2000
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