1. What is p53?
P53 is a tumor suppressor gene that plays a role in maintaining genomic stability and controlling apoptosis. During the cell cycle, it can arrest cells at the G1/S checkpoint and activate DNA repair mechanisms. It is the most mutated gene in cancer. In unstressed cells, p53 usually exists at low levels in an inactive form, being bound to Mdm2.
2. FAQs and p53
a. I fail to detect p53 by western blotting
Basal levels of wild-type p53 in untreated cells can be low. Try to load more cell lysate and use a positive control – a lysate of cells treated with DNA-damaging agents should increase p53 levels.
b. I fail to detect p53 in some cell lines by western blotting
Various p53 mutations are present in cancer cell types. If mutations cause truncations/deletions some monoclonal antibodies may no longer recognize mutated p53. You have more chances of detecting various p53 mutants with our polyclonal antibody.
c. I can detect more than one band ~50 kDa size / different cell lines give bands at slightly different size
p53 is a subject of post-translational modifications (http://p53.free.fr/p53_info/p53_modifications.html) and more than one isoform may be expressed (http://p53.free.fr/p53_info/p53_isoforms.html). Also, it is possible that your cell line of interest expresses one allele with mutated p53 with altered molecular weight.