Distal Sox Binding Elements of the αB-Crystallin Gene Show Lens Enhancer Activity in Transgenic Mouse Embryos

αB-Crystallin, a member of the small heat shock protein (sHSP) family, is expressed in various tissues including lens, heart, and skeletal muscle. Previously we identified the gene of HSPB2, another member of the sHSP family, located 1-kb upstream of the αB-crystallin gene in a head-to-head manner. In the present study, we found a highly conserved region of 220 bp approximately 2.4-kb upstream of the αB-crystallin gene and examined its role in expression of the αB-crystallin gene. Transgenic mice containing 3 kb of the upstream sequence of the αB-crystallin gene showed lacZ reporter gene expression in the lens as well as the myotome and heart on embryonic day 12.5. Deletion analysis revealed that the -2656/-2267 region including the conserved region with four putative Sox binding elements (E1-E4) exhibits lens enhancer activity toward the αB-crystallin promoter. Gel shift assays showed that the Sox1 and Sox2 proteins preferentially bound to E2 and E4. Moreover, disruption of E2 and E4 abolished the reporter gene expression in the lens. These results indicate that the newly identified enhancer with Sox elements activates the αB-crystallin promoter in the lens, although they are separated by the entire HSPB2 gene.