title: Heterogeneous nuclear ribonucleoprotein A1 regulates rhythmic synthesis of mouse Nfil3 protein via IRES-mediated translation.
abstract: Nuclear factor, interleukin 3, regulated (Nfil3, also known as E4 Promoter-Binding Protein 4 (E4BP4)) protein is a transcription factor that binds to DNA and generally represses target gene expression. In the circadian clock system, Nfil3 binds to a D-box element residing in the promoter of clock genes and contributes to their robust oscillation. Here, we show that the 5'-untranslated region (5'-UTR) of Nfil3 mRNA contains an internal ribosome entry site (IRES) and that IRES-mediated translation occurs in a phase-dependent manner. We demonstrate that heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) binds to a specific region of Nfil3 mRNA and regulates IRES-mediated translation. Knockdown of hnRNP A1 almost completely abolishes protein oscillation without affecting mRNA oscillation. Moreover, we observe that intracellular calcium levels, which are closely related to bone formation, depend on Nfil3 levels in osteoblast cell lines. We suggest that the 5'-UTR mediated cap-independent translation of Nfil3 mRNA contributes to the rhythmic expression of Nfil3 by interacting with the RNA binding protein hnRNP A1. These data provide new evidence that the posttranscriptional regulation of clock gene expression is important during bone metabolism.
authors.affiliation: Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.
authors.forename: Hyo-Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.
authors.forename: Hwa-Rim
authors.initials: HR
authors.lastname: Lee
authors.affiliation: Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Seo
authors.affiliation: Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.
authors.forename: Hye Guk
authors.initials: HG
authors.lastname: Ryu
authors.affiliation: Division of Bio-Technology and Convergence, Daegu Haany University, Gyeongsan, Gyeongsangbuk-do, Korea.
authors.forename: Kyung-Ha
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, School of Dentistry, Kyungpook National University, Daegu, Korea.
authors.forename: Do-Yeon
authors.initials: DY
authors.lastname: Kim
authors.affiliation: Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.|Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, Korea.
authors.forename: Kyong-Tai
authors.initials: KT
authors.lastname: Kim
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D057906:Circadian Clocks; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000067556:Internal Ribosome Entry Sites; D051379:Mice; D010012:Osteogenesis; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D050436:Regulatory Elements, Transcriptional; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D050976:Basic-Leucine Zipper Transcription Factors; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D000067556:Internal Ribosome Entry Sites; C497441:Nfil3 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D002118:Calcium