Characterization of the c-Myb-responsive region and regulation of the human type I collagen alpha 2 chain gene by c-Myb.
We have characterized the role of c-Myb and B-Myb in the regulation of human type I collagen alpha2 chain gene expression in fibroblastic cells. We have identified four Myb-binding sites (MBSs) in the promoter. Transactivation assays on wild type and mutant promoter-reporter constructs demonstrated that c-Myb, but not B-Myb, can transactivate the human type I collagen alpha 2 chain gene promoter via the MBS-containing region. Electrophoretic mobility shift assay experiments showed that c-Myb specifically binds to each of the four MBS; however, the mutagenesis of site MBS-4 completely inhibited transactivation by c-Myb, at least in the full-length promoter. In agreement with these results, c-myb(-/-) mouse embryo fibroblasts (MEFs) showed a selective lack of expression of type I collagen alpha 2 chain gene but maintained the expression of fibronectin and type III collagen. Furthermore, transforming growth factor-beta induced type I collagen alpha 2 chain gene expression in c-myb(-/-) MEFs, implying that the transforming growth factor-beta signaling pathway is maintained and that the absence of COL1A2 gene expression in c-myb(-/-) MEFs is a direct consequence of the lack of c-Myb. The demonstration of the importance of c-Myb in the regulation of the type I collagen alpha 2 chain gene suggests that uncontrolled expression of c-Myb could be an underlying mechanism in the pathogenesis of several fibrotic disorders.
Luchetti
Michele M
MM
Laboratorio di Medicina Molecolare, Istituto di Clinica Medica, Ematologia ed Immunologia Clinica, Università di Ancona, 60020 Ancona, Italy. mickey@deanovell.unian.it
Paroncini
Paolo
P
Majlingovà
Petra
P
Frampton
Jon
J
Mucenski
Michael
M
Baroni
Silvia Svegliati
SS
Sambo
Paola
P
Golay
Josee
J
Introna
Martino
M
Gabrielli
Armando
A
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D024042:Collagen Type I / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D020598:Proto-Oncogene Proteins c-myb / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012867:Skin / Q000378:metabolism
D024042:Collagen Type I; D017931:DNA Primers; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins