Question

You are studying a tumor suppressor gene in the cells from a biopsy of a cancer patient and find that these cells lack the activity of the protein encoded by this gene. You proceed to sequence the genome of these cancer cells. To your initial surprise you find that the sequence of the genes encoding this tumor suppressor and all of the genes involved in its transcriptional regulation are undamaged. What could be going on?

Answer 1

1. Many proteins undergo post-translational modifications for their complete activity.

I think this tumor suppressor gene (undamaged at gene level) might have some defect in post-translational modification to get its full activity.

2. There may be some defect in the post-transcriptional modification leading to the production of non-functional protein product.

3. The protein product might have an inhibitor that always bind to the protein and promotes its degradation. In this scenario, even if everything is okay with transcription and translation, protein's degradation rate will be increased.