About p53 all are true except
Wild type p53 is associated with childhood tumours Wild type 53 is the normal (non mutated form of p53). The normal p53 gene is a tumour suppressor gene that prevents the development of tumours. When wild/normal p53 gene undergoes some mutation, it is called the mutant p53 gene. Mutant p53 gene is associated with various human cancers. - A little over 50% human tumours contain mutation in this gene. - Homozygous loss of p53 occurs in viually every type of cancer including carcinomas of the lung, colon and breast. p53 Guardian of genome p53 gene is located on chromosome 17Q. It is a tumour suppressor gene. "p53 acts as a molecular policemean that prevents the propagation of genetically damaged cell". - p53 gene product i.e., p53 protein is a DNA binding protein in the nucleus, when called into action, it controls the transcription of several other genes. The major functional activities of the p53 protein are: ? Activation of temporary cell cycle arrest (quiescence) -p53 induces transcription of p21deg, a CDK inhibitor. - p21 inhibit cyclin D-CDK-4 e complex leading to arrest of cell cycle late in G1 phase. - This allows time for DNA repair (1. DNA repair p53 helps in DNA repair not only by allowing time for DNA repair but also by directly inducing the transcription of GADD 45Q (growth arrest and DNA damage). - GADD 45 encodes a protein that is involved in DNA repair. - If DNA damage is repaired successfully, p53 activates MDM 2 which in turn causes degradation of p53. This MDM-2 induced degradation of p53 causes relieve in cell cycle block. Triggering of programmed cell death p53 directs the transcription of several pro-apoptotic genes such as BAX and PUMA (approved name BBC3) and induces apoptosis. Induction of pennanent cell cycle arrest (quiescent) p53 can also cause permanent cell cycle arrest. It is characterized by specific changes in morphology and the exact mechanism is not known.
Encodes 53k Da protein
Located on Chr. 17
Arrests cell cycle at GI phase
Wild type p53 is associated with childhood tumors.