title: Protein-protein interaction among hnRNPs shuttling between nucleus and cytoplasm.
abstract: Heterogeneous nuclear ribonucleoproteins (hnRNPs) are involved in several RNA-related biological processes such as transcription, pre-mRNA processing, mature mRNA transport to the cytoplasm, and translation. About 20 major hnRNPs from A1 to U are known. Among them, hnRNP A, D, E, I, and K are known to shuttle between the nucleus and the cytoplasm. hnRNP E2 has been seen to stabilize alpha-globin mRNA and to enhance polioviral mRNA translation. hnRNP K modulates transcription and translation of some mRNAs. hnRNP I and its homologue hnRNP L have been suggested to enhance translation of some IRES-dependent mRNAs. In order to better understand the molecular mechanisms of the biological functions of hnRNPs, we investigated protein-protein interactions of six hnRNPs (hnRNP A1, C1, E2, I, K, and L) using the yeast two-hybrid system and in vitro co-precipitation assays. All of the hnRNPs tested exerted homomeric interactions, and hnRNP E2, I, K, and L interacted with each other. In the case of hnRNP E2 and hnRNP K, the N-terminal half of the proteins containing two KH (K homologous) domains were required for protein-protein interaction, and the second quarter of hnRNP I and hnRNP L containing RRM2 (RNA recognition motif 2) was essential for protein-protein interaction. hnRNP A1 and C1 did not form complexes with other hnRNPs in our assay systems. This suggests that the hnRNPs could fall into two groups: one group, including hnRNP A1 and C1, involved in hnRNP core complex formation and another group, including hnRNP E2, I, K, and L, involved in a variety of RNA-related biological processes. Different combinations of the proteins of the second group may facilitate different biological processes in conjunction with other factors.
authors.affiliation: Department of Life Science, Pohang University of Science and Technology, Hyoja-Dong San31, Pohang, Kyungbuk, 790-784, Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: B
authors.initials: B
authors.lastname: Hahm
authors.forename: Y K
authors.initials: YK
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Choi
authors.forename: S K
authors.initials: SK
authors.lastname: Jang
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D019281:Dimerization; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034664:Heterogeneous-Nuclear Ribonucleoprotein L; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D008954:Models, Biological; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D017384:Sequence Deletion / Q000235:genetics; D013379:Substrate Specificity; D020798:Two-Hybrid System Techniques; D015003:Yeasts
chemical_list: C439788:C1 HNRNP; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034664:Heterogeneous-Nuclear Ribonucleoprotein L; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins