Transcriptional control by nuclear receptors

Area of Science:

• Molecular Biology
• Genetics
• Endocrinology

Background:

• Steroid hormones regulate gene expression through intracellular receptors.
• Receptors are inactive when unbound, associated with proteins like hsp90.
• Gene regulation involves induction or repression of specific genes.

Purpose of the Study:

• To elucidate the mechanisms of gene regulation by steroid hormone receptors.
• To investigate the roles of specific DNA elements and transcription factors in hormone-mediated gene expression.
• To understand how glucocorticoids repress gene expression.

Main Methods:

• Analysis of mouse mammary tumor virus (MMTV) promoter activity.
• Investigation of hormone-responsive elements (HREs) and nucleosome phasing.
• Study of transcription factor binding (nuclear factor I, OTF-1) and DNA binding competition.
• Examination of receptor interactions with AP1 complex components (Jun, Fos).

Main Results:

• MMTV induction requires receptor binding to HREs within phased nucleosomes.
• Changes in chromatin structure and transcription factor binding (NF-I, OTF-1) correlate with receptor binding.
• OTF-1 binding to octamer motifs is crucial for progesterone receptor-mediated MMTV induction.
• Glucocorticoid repression involves DNA binding competition or interaction with the AP1 complex.

Conclusions:

• Steroid hormone receptors mediate gene regulation through diverse mechanisms.
• Specific DNA sequences and transcription factors play critical roles in hormone signaling.
• Understanding these pathways is key to comprehending gene expression control.