title: Mutation of the 5'-untranslated region stem-loop structure inhibits α1(I) collagen expression in vivo.
abstract: Type I collagen is a heterotrimeric extracellular matrix protein consisting of two α1(I) chains and one α2(I) chain. During liver fibrosis, activated hepatic stellate cells (HSCs) are the major source of the type I collagen that accumulates in the damaged tissue. Expression of α1(I) and α2(I) collagen mRNA is increased 60-fold compared with quiescent stellate cells and is due predominantly to post-transcriptional message regulation. Specifically, a stem-loop structure in the 5'-untranslated region of α1(I) collagen mRNA may regulate mRNA expression in activated HSCs through its interaction with stem-loop binding proteins. The stem-loop may also be necessary for efficient production and folding of the type I collagen heterotrimer. To assess the role of the stem-loop in type I collagen expression in vivo, we generated a knock-in mouse harboring a mutation that abolished the stem-loop structure. Heterozygous and homozygous knock-in mice exhibited a normal phenotype. However, steady-state levels of α1(I) collagen mRNA decreased significantly in homozygous mutant MEFs as well as HSCs; intracellular and secreted type I collagen protein levels also decreased. Homozygous mutant mice developed less liver fibrosis. These results confirm an important role of the 5' stem-loop in regulating type I collagen mRNA and protein expression and provide a mouse model for further study of collagen-associated diseases.
authors.affiliation: From the Departments of Biochemistry and Biophysics and.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Parsons
authors.affiliation: the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306-4300, and.
authors.forename: Branko
authors.initials: B
authors.lastname: Stefanovic
authors.affiliation: the Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, California 92093.
authors.forename: Ekihiro
authors.initials: E
authors.lastname: Seki
authors.affiliation: the Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, California 92093.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Aoyama
authors.affiliation: Genetics and.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Latour
authors.affiliation: From the Departments of Biochemistry and Biophysics and.
authors.forename: William F
authors.initials: WF
authors.lastname: Marzluff
authors.affiliation: the Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7080.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Rippe
authors.affiliation: the Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, California 92093. Electronic address: dbrenner@ucsd.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Brenner
mesh_terms: D020121:5' Untranslated Regions / Q000502:physiology*; D000818:Animals; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D055879:Gene Knock-In Techniques; D055166:Hepatic Stellate Cells / Q000378:metabolism*; D006801:Humans; D008103:Liver Cirrhosis / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008817:Mice, Mutant Strains; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis / Q000502:physiology; D020871:RNA Stability / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D020121:5' Untranslated Regions; D024042:Collagen Type I