Question

What is the most likely intracellular location in which a human protein implicated in basal skin cell cancer will reside in a human basal skin cell? Explain your logic.

Do you believe this protein will physically interact with Signal Recognition Particle? Explain.

Answer 1

P53 protein is located in the nucleus of the all the cells in the human body. It decides whether the damaged DNA has to be repaired or undergo apoptosis. P53 protein stimulates and activates them to repair the damage. If the DNA damage cannot be repaired, then this protein directs the cell to stop dividing and initiates the signaling pathway that leads to cell apoptosis. Therefore, by stopping DNA damaged cells from proliferation, this protein can prevent the tumor growth.

Mutations in the tumor suppressor gene p53 in arsenic exposed skin cells also were found to be causing skin cancer. Arsenic generates reactive oxygen species and leads to oxidative DNA damage. Arsenic is found to function as a co-mutagen and block the repair of DNA damage that is initiated by other mutagens like UV rays. Another research study also showed that Arsenic blocks the gene expression of ERCC1, XPF and XPB that are involved in nucleotide excision repair.          

There must be a series of genetic changes that should occur before the affected cell gets transferred into a cancerous one. If a normal cell is mutated, the damaged one will be programmed to die. So, skin cancer will persist and develop only when the affected cell overcomes apoptosis and divides profusely along with the genetic damage.

The unrepaired or mis-repaired pyrimidine dimers usually occur in the tumor suppressor gene, p53 in the skin cancers. This mutation will impair the protective function of p53 gene. Normally, the p53 protein will pause the cell cycle so that DNA damage is repaired before cell replication occurs. If the same function does not happen, then the protein leads to cell apoptosis pathway. It is estimated that 50 percent of human basal cell carcinomas and 90 percent of squamous cell carcinomas are due to UV-specific p53 mutations. So, these mutations are commonly observed in the skin cancer patients. Mutations in PCTH tumor suppressor gene is also found to be resulting in uncontrolled growth of keratinocytes or basal cell carcinoma development.