p63, also know as TP63 (tumor protein p63) is encoded by the TP63 gene. It is also part of the p53 family along with p53 and p73. It was discovered in 1998 as a p53-related orthologs in mouse and human cells. It is also believed to be a tumor suppressor gene Similarly to p53 and p73, p63 also has domains that are highly conserved across the family. Because of this homology, it is believed that the three genes in the p53 family have the same functions. However, after studying the genes more specifically and carefully, it was been shown that even though the genes may performs some of the same functions, they each have unique physiological roles. p63 has been associated more with have a developmental role rather than a tumor suppressing role. All three genes can cause cell cycle arrest and apoptosis, but like p73, there is alternative splicing for p63 that produces different isoforms of p63. α forms contain the sterile alpha motif (SAM) that is responsible for mediating protein-protein interactions.
The structure of p63 seems to be more similar to the structure of p73 than to p53. p63 has a transactivation domain (TA), a DNA binding domain (DBD) and an oligomerization domain (OD) that are all highly conserved with the corresponding domains in p53 and p73. The protein is composed of 15 exons and various isoforms of protein exist. Isoforms containing that transactivation domain as known as TA forms and are the full-length protein TAp63, while isoforms that do not have the transactivation domain are called ΔN forms, ΔNp63. Each form can undergo alternative splicing that produces three different C-termini forms, α, β, or γ  Additionally, ΔNp63α also has a sterile alpha motif (SAM) interacting domain at its C-terminus that is responsible for mediating protein-protein interactions. The ΔNp63 isoform of p63, like the ΔNp73 isoform of p73, does not have the N-terminal TA domain and seems to be the main negative inhibitor of TAp63 as well as other family members of the p53 family, similar to role of the ΔNp73 isoform.
- Natalie A Little, Aart G Jochemsen, p63, The International Journal of Biochemistry & Cell Biology, Volume 34, Issue 1, January 2002, Pages 6-9, ISSN 1357-2725, 10.1016/S1357-2725(01)00086-3.(http://www.sciencedirect.com/science/article/pii/S1357272501000863)
- Vincenzo Graziano, Vincenzo De Laurenzi, Role of p63 in cancer development, Biochimica et Biophysica Acta (BBA) - Reviews on Cancer, Volume 1816, Issue 1, August 2011, Pages 57-66, ISSN 0304-419X, 10.1016/j.bbcan.2011.04.002.(http://www.sciencedirect.com/science/article/pii/S0304419X11000187)
- Melino, G. "P63 Is a Suppressor of Tumorigenesis and Metastasis Interacting with Mutant P53." Cell Death and Differentiation 18.9 (2011): 1487-499. PubMed Central® (PMC). US National Library of Medicine. Web. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3178431/>.
- Nekulova, Marta, Jitka Holcakova, Philip Coates, and Borivoj Vojtesek. "The Role of P63 in Cancer, Stem Cells and Cancer Stem Cells." Cellular & Molecular Biology Letters 16.2 (2011): 296-327.