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The new collagen gene COL27A1 contains SOX9-responsive enhancer elements
Elizabeth Jenkins1, Jennie B Moss, James M Pace
1Department of Microbiology and Molecular Biology, Brigham Young University, 591 WIDB, Provo, Utah 84602, USA.
Summary
SOX9, a key regulator of cartilage development, directly activates the newest collagen gene, COL27A1. This activation requires SOX9 to bind as a dimer to specific DNA sequences within the COL27A1 gene, highlighting its role in chondrogenesis.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- COL27A1 encodes type XXVII collagen, a recently identified collagen.
- COL27A1 expression is prominent in developing cartilage and other tissues.
- Understanding COL27A1 gene regulation is crucial for cartilage biology.
Purpose of the Study:
- To investigate transcriptional regulatory mechanisms of COL27A1 in cartilage.
- To determine if SOX9, a chondrogenesis regulator, activates COL27A1 expression.
Main Methods:
- Analysis of the first intron of COL27A1 for Sox consensus sequences.
- Reporter plasmid assays to test enhancer activity in chondrocytic cells and fibroblasts.
- Electrophoretic mobility shift assays (EMSA) to assess SOX9 binding.
- Site-directed mutagenesis to investigate the role of Sox sites and SOX9 dimerization.
Main Results:
- Two distinct DNA elements within the COL27A1 first intron exhibited enhancer activity in chondrocytes.
- These elements specifically bound SOX9 protein.
- SOX9 binding and enhancer activity were dependent on paired Sox sites, indicating dimeric SOX9 binding.
- Enhancer activity was observed in fibroblasts only upon co-transfection with a SOX9 expression plasmid.
- Mutating either Sox site within a pair abolished SOX9 binding and enhancer function.
Conclusions:
- SOX9 acts as a transcriptional activator for the COL27A1 gene.
- Dimeric binding of SOX9 to specific intronic elements is essential for COL27A1 activation in chondrocytes.
- These findings reveal a novel regulatory mechanism for COL27A1 and underscore SOX9's role in chondrogenesis.