Response elements of the androgen-regulated C3 gene.

Intron and 5'-flanking regions of the androgen-regulated C3 subunit gene contain potential cis-acting transcription control sequences including several 15-base pair (bp) partial palindromes resembling response elements for glucocorticoid (GRE) and progesterone (PRE) receptors. Specific DNA binding of the androgen receptor (AR) and androgen-dependent activation of transcription indicate that some of these GRE/PRE-like sequences are capable of functioning as androgen response elements (ARE). A 0.3-kilobase pair (kbp) 5'-flanking fragment including the promoter region contains one such sequence (element A) and a 0.5-kbp region of the first intron contains two sequences (elements B and C). Androgen-dependent enhancement of transcription was assayed by cotransfection of CV1 cells with a rat AR expression vector, pCMVrAR, and C3 genomic fragments or synthetic elements cloned into the reporter vector ptkCAT. Enhancement of chloramphenicol acetyltransferase activity with the 0.5-kbp first intron fragment was 16 +/- 4-fold, while with the 0.3-kbp 5'-flanking fragment no response was detected and element C alone was greater than B or A. Binding of AR in the mobility shift assay correlated with androgen-dependent enhancement of chloramphenicol acetyltransferase activity. The intensity of transcriptional enhancement with the 0.5-kbp intron fragment suggested that other regulatory sequences within this intron region potentiated the ARE activities of elements B and C. ARE activity of the strongest C3 gene response element (C) was similar to that of a potent GRE (element M) of the mouse mammary tumor virus gene.