CHICKEN BETA-B1 CRYSTALLIN - GENE SEQUENCE AND EVIDENCE FOR FUNCTIONAL CONSERVATION OF PROMOTER ACTIVITY BETWEEN CHICKEN AND MOUSE

The complete sequence was determined for the chicken beta B1-crystalli n gene and 2.2 kbp of its 5' flanking region; the chicken gene was the n compared to its rat orthololog. Although both have a 5' non-coding e xon followed by 5 protein coding exons, the chicken gene is only 2.2 k bp while the rat gene is 13.6 kpb due to longer introns. The coding ex ons of the chicken beta B1-crystallin gene, like those or the rat and other beta-crystallin genes, each correspond to one of the four 'Greek key' motifs of the encoded protein. The only obvious similarity betwe en the 5' flanking sequences of the chicken and rat beta B1-crystallin gene is associated with the TATA box. A CR1 repetitive element is pre sent at positions -559 to -730 of the chicken beta B1-crystallin gene. In vivo footprinting using dimethyl sulfate/ligation mediated PCR sho wed that the PL-1 (-116/-102), PL-2 (-90/-76), OL-2 (-75/-68) and OL-1 (-125/-118) control elements identified previously (Roth et al. (1991 ) Mol. Cell. Biol. 11, 1488-1499) bind proteins within the chromatin o f cultured embryonic chicken lens cells. Both -2448/+30 and -434/+30 p romoter fragments from the chicken beta B1-crystallin gene directed le ns-specific CAT gene expression in a copy number and position independ ent manner in transgenic mice. These data indicate that the structure and lens-specific expression of this gene are highly conserved althoug h, like other crystallin genes, the 5' flanking sequences have diverge d appreciably during evolution.