Transcriptional control by steroid hormones

Area of Science:

• Molecular Biology
• Gene Regulation
• Endocrinology

Background:

• Steroid hormones regulate gene expression through intracellular receptors.
• Unliganded receptors are kept inactive by unknown mechanisms, possibly involving protein interactions.
• Gene induction by hormones requires receptor binding to specific DNA sequences called hormone-responsive elements (HREs).

Purpose of the Study:

• To investigate the mechanisms of gene regulation by steroid hormones, focusing on the mouse mammary tumor virus (MMTV) promoter.
• To understand the role of transcription factors and chromatin structure in hormone-induced gene expression.

Main Methods:

• Analysis of hormone receptor binding to the MMTV hormone-responsive element (HRE).
• Investigation of chromatin structure changes upon hormone treatment.
• Assessing the role of transcription factors Nuclear Factor I and OTF-1 in MMTV gene induction.

Main Results:

• Hormone receptor binding to the MMTV HRE is cooperative and requires multiple binding sites.
• Hormone treatment induces chromatin structure changes and recruits transcription factors like Nuclear Factor I.
• While Nuclear Factor I is a basal transcription factor, OTF-1 binding to octamer motifs is crucial for progesterone receptor-mediated MMTV induction.

Conclusions:

• Steroid hormone-induced gene regulation involves complex interactions between hormone receptors, HREs, and transcription factors.
• Chromatin remodeling plays a significant role in mediating hormonal effects on gene expression.
• OTF-1 is essential for the stimulatory effect of progesterone receptor on MMTV transcription, highlighting its role beyond basal transcription.