title: Translational control of collagen prolyl 4-hydroxylase-alpha(I) gene expression under hypoxia.
abstract: Hypoxia is a pro-fibrotic stimulus, which is associated with enhanced collagen synthesis, as well as with augmented collagen prolyl 4-hydroxylase (C-P4H) activity. C-P4H activity is controlled mainly by regulated expression of the alpha C-P4H subunit. In this study we demonstrate that the increased synthesis of C-P4H-alpha(I) protein in human HT1080 fibroblasts under long term hypoxia (36 h, 1% oxygen) is controlled at the translational level. This is mediated by an interaction of RNA-binding protein nucleolin (approximately 64 kDa form) at the 5'- and 3'-untranslated regions (UTR) of the mRNA. The 5'/3'-UTR-dependent mechanism elevates the C-P4H-alpha(I) expression rate 2.3-fold, and participates in a 5.3-fold increased protein level under long term hypoxia. The interaction of nucleolin at the 5'-UTR occurs directly and depends on the existence of an AU-rich element. Statistical evaluation of the approximately 64-kDa nucleolin/RNA interaction studies revealed a core binding sequence, corresponding to UAAAUC or AAAUCU. At the 3'-UTR, nucleolin assembles indirectly via protein/protein interaction, with the help of another 3'-UTR-binding protein, presumably annexin A2. The increased protein level of the approximately 64-kDa nucleolin under hypoxia can be attributed to an autocatalytic cleavage of a high molecular weight nucleolin form, without alterations in nucleolin mRNA concentration. Thus, the alteration of translational efficiency by nucleolin, which occurs through a hypoxia inducible factor independent pathway, is an important step in C-P4H-alpha(I) regulation under hypoxia.
authors.affiliation: Charité, Universitätsmedizin Berlin, Institut für Vegetative Physiologie, D-10117 Berlin, Germany. michael.faehling@charite.de
authors.forename: Michael
authors.initials: M
authors.lastname: Fähling
authors.forename: Ralf
authors.initials: R
authors.lastname: Mrowka
authors.forename: Andreas
authors.initials: A
authors.lastname: Steege
authors.forename: Grit
authors.initials: G
authors.lastname: Nebrich
authors.forename: Andrea
authors.initials: A
authors.lastname: Perlewitz
authors.forename: Pontus B
authors.initials: PB
authors.lastname: Persson
authors.forename: Bernd J
authors.initials: BJ
authors.lastname: Thiele
mesh_terms: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008433:Mathematics; D008962:Models, Theoretical; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D000097796:Nucleolin
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010750:Phosphoproteins; D011393:Procollagen-Proline Dioxygenase; D021122:Protein Subunits; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000097796:Nucleolin