5 '-upstream structure of the gene coding for chicken riboflavin-binding protein and its relation to estrogen induction

To elucidate the mechanism of the estrogen-dependent induction of chicken r iboflavin-binding protein (RfBP), we analyzed the 5'-upstream structure of its gene, A noncoding exon exists there, and around this sequence, 9 widely spaced half-palindromic estrogen-response element (ERE) motifs (5'-GGTCA o r 5'-TGACC) were found. Furthermore, an imperfect ERE-like palindromic sequ ence (5'-ATGTCANNNTGACAT-3') was also found at the 2.25 kb upstream region. No consensus palindromic ERE was observed. Ey luciferase reporter assay, t he regions containing the half ERE motifs and the imperfect ERE showed estr ogen-dependent enhancer activities, suggesting that these two characteristi c sequences might confer estrogen-inducibility upon the chicken RfBP gene. However the activities were longer than that of a consensus ERE, It remains uncertain whether these sequences act cooperatively.