MyoD is a transcriptional activator that turns on the expression of several muscle-specific genes in human cells. The Id gene product inhibits MyoD action. a. One possibility is that the Id protein directly represses the expression of these muscle-specific genes. Explain how Id would function if it were a repressor. b. Another possibility is that Id inhibits musclespecific gene transcription indirectly, by preventing MyoD function. Explain how Id could function as an indirect repressor. c. Suppose you know the amino acid sequence of the Id protein. How might this information support the hypothesis in part (a) or in part (b)

a) Myod is an activator, which is responsible for the differentiation in the muscles. If the gene is a repressor, it will bind to MyoD and a complex will be produced, which will inhibit DNA binding and alter the transcription capacity of genes in messenger RNA.

b) If the Id gene an indirect inhibitor, it would not bind to the DNA but to the repressor gene, in this way it will allow the activation of the transcription factor of the repressor. Therefore, the repressor would join the promoter and this process is restricted.

c) Knowing the amino acid sequence of Id, it would be easy to find the function of said gene. Knowing the sequence, the functions of the gene would be known, as promoter, activator, and repressor.

Explanation:

a) The Id gene acting as a repressor would bind to DNA at the site where MyoD has bound, therefore, said gene would inhibit the action of MyoD indirectly.

b) The Id gene inhibits the action of MyoD indirectly, resulting in the formation of an inactive heterodimer.

c) Knowing the amino acid sequence of the Id gene would lead to the conclusion that the MyoD as the Id gene would have the same dimerization domain.

luisvaschetto luisvaschetto · Answer 2 · 2021-12-14T20:09:41+01:00

A direct repressor directly interacts with regulatory nucleotide (genomic) regions of the target gene, while an indirect repressor inhibits the expression of TFs that promote target gene expression.

A direct repressor is a molecule (eg., a protein) that binds to regulatory regions of the target gene (e.g., promoter regions), thereby preventing the synthesis of its cognate messenger RNA (mRNA).

Conversely, an indirect repressor is a molecule that inhibits the upstream signaling pathway of the target gene, thereby preventing the binding of Transcription Factors (TFs) or the RNA polymerase (RNApol) to promoter/enhancer regions.

In this case, it is possible to determine the repressive mechanism by triggering mutations in the Id protein domain that binds with the regulatory nucleotide sequence of TFs localized upstream in the signaling pathway of the target gene (MyoD).

If the Id protein is an indirect repressor, then the lack of inhibition of upstream TFs that promote the MyoD-mediated signaling pathway will be equally able for repressing the expression of the target gene.

In conclusion, a direct repressor directly interacts with regulatory nucleotide (genomic) regions of the target gene, while an indirect repressor inhibits the expression of TFs that promote target gene expression.

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