Question

Choose correct answers: Which of the following are true of nuclear receptors?

Question 7 options:

A	initially in cytoplasm and transition to nucleus
B	are often bound by steroid hormones
C	are often bound by peptide signals like insulin
D	act as G coupled proteins
E	act as transcription factors
F	always found in the nucleus
G	are likely to have effects within seconds
H	are likely to have effects within hours
I	increase concentrations of secondary messengers
J	alter expression of select genes

Answer 1

A. True. Nuclear receptors are initially present in the cytosol and are translocated to the nucleus upon activation.

B. True. Nuclear receptors are activated upon binding to a hormone mostly steroid hormones and followed by the dissociation of heat shock proteins, dimerization and translocation to the nucleus.

C. True. Peptide signals like insulin bind to hormone nuclear receptors and cause their activation

D. False. Nuclear receptors do not act as G-coupled proteins. They are different however recent studies have shown nucler localization of G-coupled receptor proteins though they usually activate receptors at cell surface level.

E. True. Nuclear receptors act as transcription factors by binding directly to DNA and thereby regulating the expression of adjacent genes.

F. False. They are not always found in the nucleus because they are usually present in the cytosol and are translocated to the nucleus upon activation by a ligand. However, an exception to this are type II nuclear receptors which are retained in the nucleus irrespective of their ligand binding status.

G. False. It is not effective within seconds as it takes hours to alter protein expression levels.

H. True. Nuclear receptors are likely to have effects within hours but it may vary from few to many hours as the process involves several intermediate process that finally cause effect on the levels of protein expression.

I. True. Secondary messengers are actually present in low concentrations in the cell and are increased rapidly upon receptor-mediated activation.

J. True. Nuclear receptors have the ability of target gene recognition and possess specificty of binding to the subset of target genes and the process is ligand specific.