title: Regulation of human COL2A1 gene expression in chondrocytes. Identification of C-Krox-responsive elements and modulation by phenotype alteration.
abstract: To identify control motifs involved in human type II collagen gene transcription in both differentiated and dedifferentiated rabbit articular chondrocytes, transient transfection experiments were performed. A 715-base pair (bp) region of the first intron (+2127/+2842), including a 153-bp sequence so far uncharacterized (+2689/+2842), was found to mediate enhancer activity. In dedifferentiated chondrocytes, this enhancer activity was shown to be less effective than in primary cultures but still present. We then demonstrated that a zinc finger protein, C-Krox, activates COL2A1 gene transcription in differentiated chondrocytes through the enhancer region, whereas in subcultured cells, it inhibited the gene activity via a 266-bp promoter. Multicopies of the C-Krox binding site were found to mediate transactivation in both primary cultures and passaged cells, whereas C-Krox overexpression inhibited transcription in dedifferentiated chondrocytes. Additionally, we showed that C-Krox binds to several cis sequences that mediate its transcriptional effects. During chondrocyte dedifferentiation, the protein levels and binding activity of C-Krox were reduced, whereas those of NF-kappaB were increased. This was not associated with variations of mRNA levels, suggesting that post-transcriptional regulatory mechanisms could be involved in C-Krox expression. These results suggest that C-Krox plays a major role in type II collagen expression and the chondrocyte phenotype modulation.
authors.affiliation: Laboratoire de Biochimie du Tissu Conjonctif, Centre Hospitalier Universitaire de Caen, Faculté de Médecine, Avenue de la Côte de Nacre, 14032, Caen Cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Ghayor
authors.forename: J F
authors.initials: JF
authors.lastname: Herrouin
authors.forename: C
authors.initials: C
authors.lastname: Chadjichristos
authors.forename: L
authors.initials: L
authors.lastname: Ala-Kokko
authors.forename: M
authors.initials: M
authors.lastname: Takigawa
authors.forename: J P
authors.initials: JP
authors.lastname: Pujol
authors.forename: P
authors.initials: P
authors.lastname: Galéra
mesh_terms: D000818:Animals; D001483:Base Sequence; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002454:Cell Differentiation; D019902:Chondrocytes / Q000378:metabolism*; D003094:Collagen / Q000235:genetics*; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D010641:Phenotype; D011817:Rabbits; D017384:Sequence Deletion; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C484225:ZBTB7B protein, human; D003094:Collagen