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.
Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0032, Japan.
Y
Y
Arao
R
R
Kuriyama
F
F
Kayama
S
S
Kato
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001693:Biological Transport, Active; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006367:HeLa Cells; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D066298:In Vitro Techniques; D036961:Matrix Attachment Region Binding Proteins; D051379:Mice; D015530:Nuclear Matrix / Q000378:metabolism*; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D017931:DNA Primers; D004268:DNA-Binding Proteins; C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C000630987:Hnrpd protein, mouse; D036961:Matrix Attachment Region Binding Proteins; D034521:Nuclear Matrix-Associated Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; C109132:SAFB protein, human