27. In an experiment it was observed that a protein was upregulated in cancer tissues (compared to control tissues) that showed correlation with disease progression. Following are a few possibilities, which can explain the above observation.
    A. A mutation could be located in the 3’UTR of the corresponding mRNA at a miRNA binding site.
    B. A mutation changes the conformation of the protein, resulting in its better stability.
    C. A mutation in the corresponding mRNA promotes ribosome read-through of the termination codon resulting in increased synthesis of the protein.
    D. A mutation in the corresponding mRNA increased the stability of the RNA due to change in secondary structure.
    Which one of the following combinations represents the most likely explanations?
    (1) A, B and C (2) B, C and D
    (3) C, D and A (4) A, B and D

The most likely explanations for the observed upregulation of a protein correlated with cancer progression are:

(4) A, B and D

Explanation

• A. Mutation in the 3’UTR at a miRNA binding site:
  Mutations here can disrupt miRNA binding, which normally represses translation or stability of the mRNA, resulting in increased protein expression.

• B. Mutation changes protein conformation leading to better stability:
  Altered protein folding or modifications can prevent degradation, increasing protein half-life and accumulation in cancer cells.

• D. Mutation increasing mRNA stability by changing secondary structure:
  More stable mRNA leads to increased translation and protein levels, contributing to upregulation.

• C. Mutation causing ribosome read-through of termination codon:
  This is a rare and less common mechanism; while it could increase protein synthesis, it is not a frequent or typical cause of upregulation in cancer.

Therefore, combinations involving A, B, and D best explain increased protein expression in cancer tissues.​