External genitalia are prominent organs showing hormone-dependent sexual differentiation. Androgen is an essential regulator of masculinization of the genital tubercle, which is the anlage of external genitalia. We have previously shown that v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB) is an androgen-inducible regulator of embryonic urethral masculinization in mice. However, it remains unclear how androgen regulates Mafb expression. The current study suggests that the Mafb 3′ untranslated region (UTR) is an essential region for its regulation by androgen. We identified 2 functional androgen response elements (AREs) in Mafb 3′UTR. Androgen receptor is bound to such AREs in 3′UTR during urethral masculinization. In addition to 3′UTR, Mafb 5′UTR also showed androgen responsiveness. Moreover, we also demonstrated that β-catenin, one of genital tubercle masculinization factors, may be an additional regulator of Mafb expression during urethral masculinization. This study provides insights to elucidate mechanisms of gene regulation through AREs present in Mafb 3′UTR for a better understanding of the processes of urethral masculinization.
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