Binding of a factor to an enhancer element responsible for the tissue-specific expression of the chicken alpha A-crystallin gene.

We have characterized a regulatory region of the chicken alpha A-crystallin gene using transfection assays, which revealed that a 84 base pair element (-162 to -79) in the 5' flanking sequence is necessary and sufficient for lens-specific expression. A multimer of this element functions as lens-specific enhancer and synergistically activates transcription from chicken alpha A-crystallin or beta-actin basal promoters fused to the CAT gene. In vivo competition experiments demonstrated that DNA sequences containing the 84 bp element reduced alpha A-crystallin-CAT fusion gene expression. A nuclear factor present exclusively in lens cells binds to the 84 bp element in the region between positions -165 and -140. Southwestern blot analysis showed that 61,000 Mr (61 x 10(3) Mr) lens nuclear protein exhibited DNA-binding activity specific to the 84 bp element. Our data suggested that the 61 x 10(3) Mr nuclear protein, and the 84 bp element that it interacts with, may be involved in regulating the alpha A-crystallin gene expression in vivo.