Consider a transcription regulatory protein that has both a nuclear localization and a nuclear export signal and is normally found both in the nucleus and in the cytosol at comparable concentrations. This protein has a high-affinity binding partner in the nucleus. Upon activation of a certain signaling pathway, the binding protein is ubiquitylated and degraded. As a result of this, ...
A) the transcription regulatory protein accumulates in the nucleus.
B) the transcription regulatory protein accumulates in the cytosol.
C) the distribution of the transcription regulatory protein does not change, but the expression of its target genes may be altered.
D) the distribution of the transcription regulatory protein does not change, and the expression of its target genes is not necessarily changed as a result of the degradation event.

Question

Quizplus · Accepted Answer

A high-affinity binding partner in the nucleus inevitably shifts the steady-state distribution of the protein toward this compartment. Once the partner is eliminated, the now-dominating export route leads to accumulation of the protein in the cytosol. An effect on gene expression does not depend on localization alone.

Consider a Transcription Regulatory Protein That Has Both a Nuclear