title: Heterogeneous nuclear ribonucleoprotein C modulates translation of c-myc mRNA in a cell cycle phase-dependent manner.
abstract: The c-myc proto-oncogene plays a key role in the proliferation, differentiation, apoptosis, and regulation of the cell cycle. Recently, it was demonstrated that the 5' nontranslated region (5' NTR) of human c-myc mRNA contains an internal ribosomal entry site (IRES). In this study, we investigated cellular proteins interacting with the IRES element of c-myc mRNA. Heterogeneous nuclear ribonucleoprotein C (hnRNP C) was identified as a cellular protein that interacts specifically with a heptameric U sequence in the c-myc IRES located between two alternative translation initiation codons CUG and AUG. Moreover, the addition of hnRNP C1 in an in vitro translation system enhanced translation of c-myc mRNA. Interestingly, hnRNP C was partially relocalized from the nucleus, where most of the hnRNP C resides at interphase, to the cytoplasm at the G(2)/M phase of the cell cycle. Coincidently, translation mediated through the c-myc IRES was increased at the G(2)/M phase when cap-dependent translation was partially inhibited. On the other hand, a mutant c-myc mRNA lacking the hnRNP C-binding site, showed a decreased level of translation at the G(2)/M phase compared to that of the wild-type message. Taken together, these findings suggest that hnRNP C, via IRES binding, modulates translation of c-myc mRNA in a cell cycle phase-dependent manner.
authors.affiliation: National Research Laboratory, Department of Life Science, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, Korea.
authors.forename: Jong Heon
authors.initials: JH
authors.lastname: Kim
authors.forename: Ki Young
authors.initials: KY
authors.lastname: Paek
authors.forename: Kobong
authors.initials: K
authors.lastname: Choi
authors.forename: Tae-Don
authors.initials: TD
authors.lastname: Kim
authors.forename: Bumsuk
authors.initials: B
authors.lastname: Hahm
authors.forename: Kyong-Tai
authors.initials: KT
authors.lastname: Kim
authors.forename: Sung Key
authors.initials: SK
authors.lastname: Jang
mesh_terms: D020121:5' Untranslated Regions; D017209:Apoptosis; D001665:Binding Sites; D019921:Biotinylation; D015152:Blotting, Northern; D002453:Cell Cycle; D002454:Cell Differentiation; D002455:Cell Division; D002469:Cell Separation; D018387:Codon, Initiator; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D016195:G2 Phase; D017930:Genes, Reporter; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008938:Mitosis; D008957:Models, Genetic; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D020121:5' Untranslated Regions; D018387:Codon, Initiator; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase