Multiple receptor domains interact to permit, or restrict, androgen-specific gene activation

Area of Science:

• Molecular Biology
• Genetics
• Endocrinology

Background:

• Highly related transcription factors direct diverse regulatory programs.
• Androgen receptor (AR) and glucocorticoid receptor (GR) recognize similar DNA elements but activate genes with distinct specificity.
• Specificity is influenced by promoter and cellular context.

Purpose of the Study:

• To assess the role of different AR and GR domains in hormone-specific gene activation.
• To investigate mechanisms underlying the precise activation of the androgen-specific sex-limited protein (Slp) gene enhancer by AR.

Main Methods:

• Creation and testing of AR-GR chimeras for enhancer activation.
• Analysis of DNA binding affinity.
• In vitro DNase I footprinting assays.
• Transactivation assays with mutant enhancers.

Main Results:

• Only specific AR-GR chimeras activated the androgen-specific Slp enhancer.
• The AR DNA binding domain, not differential DNA affinity, was crucial for activating the AR-specific target.
• AR N-terminus and ligand binding domain enhanced cooperativity at multiple, weak HREs.
• AR N-terminal subdomains relieved inhibitory effects of the ligand binding domain.

Conclusions:

• Intrinsic AR functions enhance steroid-specific gene activation by evading negative regulation and promoting cooperativity.
• Intra- and inter-receptor domain interactions contribute to transcriptional specificity.
• Subtle differences in AR and GR domain behavior enforce specificity within the context of non-receptor factors.