Necdin interacts with the ribonucleoprotein hnRNP U in the nuclear matrix.
Necdin is expressed predominantly in terminally differentiated neurons, and its ectopic expression suppresses cell proliferation. We screened a cDNA library from neurally differentiated embryonal carcinoma P19 cells for necdin-binding proteins by the yeast two-hybrid assay. One of the positive clones contained cDNA encoding a carboxyl-terminal portion of heterogeneous nuclear ribonucleoprotein U (hnRNP U), a nuclear matrix-associated protein that interacts with chromosomal DNA. We isolated cDNA encoding full-length mouse hnRNP U to analyze its physical and functional interactions with necdin. The necdin-binding site of hnRNP U was located near a carboxyl-terminal region that mediated the association between hnRNP U and the nuclear matrix. In postmitotic neurons, endogenously expressed necdin and hnRNP U were detected in the nuclear matrix and formed a stable complex. Ectopically expressed necdin was concentrated in the nucleoli, but coexpressed hnRNP U recruited necdin to the nucleoplasmic compartment of the nuclear matrix. Furthermore, under the same conditions necdin and hnRNP U cooperatively suppressed the colony formation of transfected SAOS-2 cells. These results suggest that necdin suppresses cell proliferation through its interaction with hnRNP U in the specific subnuclear structure.
Taniura
Hideo
H
Division of Regulation of Macromolecular Functions, Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan. hideo@protein.osaka-u.ac.jp
Yoshikawa
Kazuaki
K
D000818:Animals; D001665:Binding Sites; D002455:Cell Division; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D051379:Mice; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology; D009474:Neurons / Q000378:metabolism; D015530:Nuclear Matrix / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012261:Ribonucleoproteins; C069766:necdin