Identification of nuclear factor delta EF1 and its binding site essential for lens-specific activity of the delta 1-crystallin enhancer.

The lens-specific reglatory element of the delta 1-crystallin enhancer lies within the core segment (Goto et al., (1990) Mol. Cell. Biol. 10, 935-964). The element was allocated within the 55 bp long HN fragment of the core. Block-wise base substitutions were introduced to the 55 bp and their effect on the enhancer activity of the multimers in lens cells was examined. By base sequence alteration of either of the contiguous blocks 5 and 6, with their original sequence of TTGCT and CACCT, respectively, enhancer activity was totally lost. A lens nuclear factor delta EF1 was found which bound specifically to the base sequences defined by the blocks. DNA binding activity very similar to delta EF1 was also found in extracts of tissues other than lens, suggesting that delta EF1 participates in lens-specific regulation through tissue-dependent modification or interaction with other factors.