A member of the Y-box protein family interacts with an upstream element in the alpha1(I) collagen gene.
Transforming growth factor beta (TGF-beta) stimulates protein complex formation on a TGF-beta response element (TAE) found in the distal portion (-1624) of the collagen alpha 1(I) promoter. To identify the fibroblast proteins in this complex, an expression library constructed from human embryonic lung fibroblasts mRNA was screened using a tetramer of TAE. Y-box binding protein (YB-1), was identified as a protein in the TAE-protein complex. The protein expressed by phage clones formed a specific complex with labeled TAE but not mutated TAE (mTAE) similar to the complex formed with nuclear protein. Nuclear protein-TAE complexes isolated from native gels contained YB-1 by Western analysis. TGF-beta treatment increased the amount of YB-1 protein in nuclear extracts, decreased its amount in cytoplasm, but did not alter the steady state levels of YB-1 mRNA. A full-length YB-1 protein expressed in human lung fibroblasts was primarily located in the nucleus with punctate staining in cytoplasmic regions. The expression of YB-1 decreased in the cytoplasm after 2 h of TGF-beta treatment. Therefore, the increased binding activity seen in TGF-beta-stimulated nuclear extracts was due primarily to relocalization of YB-1 from the cytoplasm to the nuclear compartment. Co-transfection of YB-1 cDNA with a collagen promoter-reporter construct caused a dose-dependent activation of collagen promoter activity in rat fibroblasts whereas the promoter with a mutation in the TAE element was not sensitive to YB-1 co-expression. In conclusion, we have identified YB-1 as a protein that interacts with a TGF-beta response element in the distal region of the collagen alpha 1(I) gene. YB-1 protein activates the collagen promoter and translocates into the nucleus during TGF-beta addition to fibroblasts, suggesting a role for this protein in TGF-beta signaling.
Sun
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Department of Biochemistry, Boston University School of Medicine, 715 Albany St., Boston, MA 02118, USA.
Hou
F
F
Panchenko
M P
MP
Smith
B D
BD
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D024042:Collagen Type I / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D024042:Collagen Type I; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D015500:Chloramphenicol O-Acetyltransferase