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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,:

1) The transcription regulatory protein accumulates in the nucleus.
2) The transcription regulatory protein accumulates in the cytosol.
3) The distribution of the transcription regulatory protein does not change, but the expression of its target genes may be altered.
4) 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.

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Final answer:

Upon ubiquitylation and degradation of the nuclear binding partner, the transcription regulatory protein is likely to accumulate in the nucleus. This accumulation happens due to a shifted concentration gradient since the regulatory protein lacks its binding partner. This event can potentially alter gene expression if the regulatory protein behaves as a transcription factor.

Step-by-step explanation:

Response to the Ubiquitylation of a Binding Partner in Protein Trafficking

When the high-affinity binding partner in the nucleus is ubiquitylated and degraded, the transcription regulatory Protein that has both a nuclear localization and a nuclear export signal will likely accumulate in the nucleus . This accumulation occurs because the ubiquitylation and subsequent degradation of the binding partner liberate the regulatory protein, facilitating its movement into the nucleus where the gradient of binding partners has now been shifted. In the absence of its binding partner, the regulatory protein is not held in the nucleus, which potentially changes the concentration gradient and drives more protein into the nucleus.

The degradation of the binding partner would not immediately lead to a change in the expression of the target genes of the regulatory protein since the presence of the regulatory protein in the nucleus was already established before the degradation. However, the accumulation of additional regulatory protein in the nucleus could eventually influence gene expression if the regulatory protein acts as a transcription factor. This regulatory protein's role in post-translational control of gene expression includes potentially influencing RNA stability or altering trans -acting element interaction.

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