PARENT SESSION
PLATFORM SESSION 4: GONADAL GENE REGULATION AND FUNCTION
Chair: Zeleznik, Tony¹, ¹
Co-chair: Bowen, Jennifer¹, ¹
Harborside B
4:30 PM-6:30 PM

(30) INTERACTIONS BETWEEN TWO TRANSCRIPTION FACTOR FAMILIES, bHLH AND CREB, IN THE REGULATION OF SERTOLI CELL DIFFERENTIATION.

Saxlund, Melissa¹, Skinner, Michael¹, ¹ Center for Reproductive Biology, Pullman, WA

ABSTRACT- Differentiation in Sertoli cells is marked by the presence of novel gene products, such as transferrin and androgen binding protein (ABP). The promoters of these genes contain response elements that control their expression. The transferrin gene has been shown to upregulate under the influence of FSH and cAMP by promoting the binding of basic helix-loop-helix (bHLH) and cAMP response element binding protein (CREB) to the E-box and CRE-like proximal region II (PRII), respectively, which interact through the CBP/p300 protein. Therefore, it is hypothesized that the interaction between the bHLH and CREB are required for optimal expression of Sertoli cell differentiated functions. To further investigate this, the ABP promoter is being studied through use of transfections, site-directed mutagenesis, and gel shifts. Transfection data indicates that cAMP and FSH upregulate the proximal 600 bp of the ABP promoter at 24 hours post-treatment (control, 50 ng/mL FSH, 0.5 mM db-cAMP, and 10% serum). A serum response is seen 72 hours post-treatment, possibly indicating a secondary activation pathway. Mutational studies of the three ABP E-boxes and PRII indicate that any one of the three E-boxes is critical for upregulation of the promoter. Since the ABP promoter contains an E-box within the PRII, gel shifts were examined and reveal a weak interaction between bHLH and CREB. Observations indicate a potential competition between the factors. Transfection data of the PRIImut supports a competitive mechanism as seen by an increase in the reporter expression when only the overlapping E-box is present. In conclusion, the ABP gene is similar to that of transferrin in that it employs both the bHLH and CREB transcription factors, but the mechanism these factors utilize may be different. The ABP gene appears to be regulated by the E-boxes present in the proximal promoter and a competitive mechanism involving one of the E-boxes and the CRE-like PRII may be critical for expression of the gene.

KEY WORDS: Sertoli cell, ABP, bHLH, CREB