Final answer:
If a cell is unable to add ubiquitin to a protein, it would result in the protein not being marked for degradation, leading to abnormal protein accumulation and disrupted cellular function. This can have consequences such as misfolded protein accumulation and dysregulated gene expression.
Step-by-step explanation:
If a cell is unable to add ubiquitin to a protein, it would most likely result in the protein not being marked for degradation. Ubiquitin acts as a flag indicating that the protein's lifespan is complete and targets it for degradation by the proteasome. Without ubiquitin, the protein would not be recognized for degradation and would continue to accumulate within the cell.
This could have several consequences. One possible outcome is the accumulation of misfolded or damaged proteins, which can lead to cellular dysfunction and disease. Another consequence is the disruption of gene expression control, as altering the longevity of proteins through ubiquitin modification is one way to regulate gene expression.
For example, in the case of the alternative protein binding to the 3' UTR of an RNA and causing its degradation, an excess of the alternative protein could disrupt normal cellular processes and lead to dysfunction. Therefore, the inability to add ubiquitin to a protein could result in abnormal protein accumulation, compromised cellular function, and dysregulated gene expression.