The androgen receptor facilitates inhibition of human dopamine transporter (DAT1) reporter gene expression by HESR1 and HESR2 via the variable number of tandem repeats

Abstract

A functional genetic polymorphism in the 3′-untranslated region (UTR) within exon 15 of the human DAT gene (DAT1) has been described. This 3′-UTR contains a variable number of tandem repeats (VNTR) 40bp in length; many association studies of psychiatric or developmental disorders with this VNTR have been conducted. We previously demonstrated that HESR1 (the Hairy/enhancer of split related transcriptional factor 1 with YRPW motif) and HESR2 reduced DAT reporter gene expression via this 3′-UTR. VNTR allele-dependent altered reporter gene expression was also observed. In the present study, we wanted to clarify the molecular characterization of HESR1 and HESR2, focusing on its cis-element and co-factor. Deletion of the VNTR domain increased reporter gene expression both with and without transfection of HESRs, suggesting that the VNTR inhibits DAT expression, and is responsive to HESRs. In the presence of transfected androgen receptor (AR), activity of the luciferase reporter with the nine-repeat allele (9r) decreased, while that with the ten-repeat allele (10r), the most frequent in the population, increased significantly. Furthermore, co-expression of HESR1 or HESR2 with AR increased the inhibitory effect of the HESRs. Our data indicate that a functional modification occurs when the HESRs are coupled with AR. This HESR–AR interaction could be the molecular basis of sexual dimorphisms in DAT expression, or other dopamine-related behavioral traits.