A new long form of c-Maf cooperates with Sox9 to activate the type II collagen gene.
A new long form of the c-Maf transcription factor (Lc-Maf) was identified and shown to interact specifically with SOX9 in a yeast two-hybrid cDNA library screening. Lc-Maf encodes an extra 10 amino acids at the carboxyl terminus of c-Maf and contains a different 3'-untranslated region compared with c-Maf. The interaction between SOX9 and Lc-Maf was further confirmed by co-immunoprecipitation and glutathione S-transferase pull-down assays, which mapped the interacting domain of SOX9 to the high mobility group box DNA binding domain and that of Lc-Maf to the basic leucine zipper motif. In situ hybridizations showed that Lc-Maf RNA was coexpressed with Sox9 and Col2a1 RNA in areas of precartilaginous mesenchymal condensations during mouse embryo development. A DNA binding site of Lc-Maf was identified at the 5'-end of a 48-bp Col2a1 enhancer element near the high mobility group binding site of SOX9. Lc-Maf and SOX9 synergistically activated a luciferase reporter plasmid containing a Col2a1 enhancer and increased the transcription of the endogenous Col2a1 gene. In summary, Lc-Maf is the first transcription factor shown to interact with Sox9, to be coexpressed with Sox9 during an early step of chondrogenesis and to cooperate with Sox9 in activating a downstream target gene of Sox9.
Huang
Wendong
W
Department of Molecular Genetics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Lu
Ni
N
Eberspaecher
Heidi
H
De Crombrugghe
Benoit
B
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019902:Chondrocytes / Q000502:physiology; D024043:Collagen Type II / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D005786:Gene Expression Regulation; D015723:Gene Library; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006801:Humans; D008223:Lymphoma; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D051257:Proto-Oncogene Proteins c-maf; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D055758:SOX9 Transcription Factor; D012733:Sex Differentiation; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D024043:Collagen Type II; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; C495607:MAF protein, human; C495608:Maf protein, mouse; D011518:Proto-Oncogene Proteins; D051257:Proto-Oncogene Proteins c-maf; D011993:Recombinant Fusion Proteins; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; C527933:Sox9 protein, mouse; D014157:Transcription Factors