Nuclear Receptors and Transcription Regulation

Questions and Answers

What is the primary function of nuclear receptors?

Regulating transcription by binding to DNA (correct)

Transporting hormones in the bloodstream

Degrading mRNA molecules

Acting as enzymes to modify DNA

Which of the following is NOT a form in which nuclear receptors can bind to response elements?

Heterodimers

Tetramers (correct)

Homodimers

Monomers

Where are steroid hormone receptors located in the absence of a ligand?

In the cell membrane

In the cytosol (correct)

In the mitochondria

In the nucleus

What occurs upon ligand binding to a steroid hormone receptor?

Heat-shock proteins dissociate from the receptor Signup and view all the answers

How do steroid receptors typically bind to DNA?

As homodimers to inverted repeats Signup and view all the answers

What defines a hormone response element (HRE)?

A specific DNA sequence that binds multiple receptors Signup and view all the answers

What are the three defining features of a response element?

Base pair sequence, orientation, spacing Signup and view all the answers

What happens to the ligand-receptor complex after it translocates into the nucleus?

It binds to the hormone-response element in DNA Signup and view all the answers

What is the role of the heat-shock protein (HSP) in relation to steroid hormone receptors?

To stabilize receptors in their inactive form Signup and view all the answers

Study Notes

Nuclear Receptors Overview

Nuclear receptors function as regulatory transcription factors.
They bind to regulatory DNA sequences known as response elements.

Binding Forms of Nuclear Receptors

Can bind as:
- Monomers: Example, steroidogenic factor-1 receptor.
- Homodimers: Example, steroid receptors.
- Heterodimers: Examples, retinoic acid receptor, thyroid hormone receptor, vitamin D receptor, and several orphan nuclear receptors.

Steroid Hormone Receptors

Located in the cytosol in an inactive form stabilized by heat-shock proteins (HSP).
Ligand binding causes dissociation of HSPs, allowing translocation to the nucleus.

Mechanism of Action in the Nucleus

The ligand-receptor complex binds to specific hormone-response elements (HRE) in DNA after nuclear translocation.
Steroid receptors bind as homodimers to inverted repeats with a three-nucleotide spacer sequence.

Characteristics of Hormone Response Elements (HRE)

HREs are specific DNA sequences recognized by receptors with high affinity.
Typically consist of two consensus hexameric half-sites.
Three critical features define a response element:
- Sequence of base pairs in each half-site.
- Number of base pairs separating the half-sites.
- Relative orientation of the half-sites.

Importance of Response Element Recognition

Each dimeric receptor must accurately identify the sequence, spacing, and orientation of the half-sites within the response element to effectively bind DNA.

Description

This quiz explores the role of nuclear receptors as regulatory transcription factors that bind to regulatory DNA sequences known as response elements. It covers the forms in which these receptors can exist, including monomers, homodimers, and heterodimers, as well as their locations and functions within the cell.