PARENT SESSION

(M442) THE REGULATION OF EXPRESSION OF MEMBERS OF THE PEA3 TRANSCRIPTION FACTOR FAMILY AND THEIR DOWNSTREAM TARGETS IN THE RAT EPIDIDYMIS.

Yang, Ling¹, Kirby, Jennifer¹, Troan, Brigid¹, Fox, Sallie¹, Hinton, Barry¹, ¹ University of Virginia, Charlottesville, Virginia

ABSTRACT- Several genes expressed in the initial segment of the epididymis depend on factors from the testis that reach the epididymis via the luminal system. These include the -glutamyl transpeptidase mRNA IV (GGT mRNA IV), 5-reductase, glutathione peroxidase 5 (GPX5) and cystatin-related epididymal specific (CRES) genes. Promoter analyses indicated that all of the genes contain several Ets DNA-binding sites. Members of the polyomavirus enhancer activator 3 (PEA3) family (PEA3, ERM, ER81) are capable of binding to Ets sites in the promoter of target genes to regulate transcription. In this study, the role of PEA3 family members in the transcription of genes regulated by testicular luminal fluid factors was evaluated. All three PEA3 family mRNAs are expressed in the principal cells of the initial segment and are dependent on testicular luminal fluid factors. PEA3 protein was localized to principal cell nuclei and displayed the highest expression in the most proximal region of the initial segment. In addition, PEA3 protein levels were severely diminished 12 hours after efferent duct ligation. A dominant-negative construct of ERM was in vivo electroporated into the initial segment to determine if PEA3 family members can regulate the transcription of other genes regulated by luminal testicular factors. Real-time PCR indicated that after expression of the dominant-negative construct for one day in the initial segment, all three PEA3 family member mRNAs were significantly decreased. In addition, GGT mRNA IV, 5-reductase, and GPX5 mRNA levels were also significantly decreased. Based on the localization and regulation of PEA3 family members, this data suggests not only that PEA3 family members regulate their own expression, but that they regulate the transcription of a subset of genes that are dependent upon testicular luminal fluid factors. Supported by Ernst Schering Research Foundation and CONRAD.

KEY WORDS: PEA3, epididymis, gene expression