True statements about P53. gene are all except ?
Ans. is 'd' i.e., Wild/non-mutated form is associated with increased risk of child-hood tumorsIt is mutated form (not non mutated form) of p53 which is associated with increased risk of tumors.o p53 gene is a tumor suppressor gene and non-mutated form of this gene prevent development of malignancy by :(i) Causing cell cycle arrest in late GI phase(ii) Inducing apoptosis(iii) Helping in DNA repairo Mutation in p53 gene causes inactivation of p53 gene and abolishen of above function that results in uncontrolled proliferation of cells and malignant transformation.o Mutation in p53 gene is the most common genetic alteration found in human Cancer.o The name p53 is in reference to its apparent molecular mass; it runs as a 53 kilodalton (Kda) protein on SDS-page. But based on calculations from its amino acid residues, p53 's mass is actually only 43.7 K Da.Following information have been added in P/e of Robbin'so p53 prevents neoplastic transformation by three interlocking mechanisms : ?1. Activation of temporary cell cycle arrest (quiescence)o It is considered as the primordial response to DNA damage.o p53 causes arrest in late GI through p2 I .o This is temporary arrest that gives the cell "breathing time" to repair DNA damage.o After DNA repair, cell cycle block is relieved by MDM-3 which degrades p53.2. Induction of permanent cell cycle arrest (senscence)o p53 induced sencence is a permanent cell cycle arrest characterized by specific changes in morphology and gene expression that differentiate it from quiescence (temporary or reversible cycle arrest).o The mechanisms of senscence is unknown, but involve epigenetic changes that result in the formation of heterochromatin at different loci throughout the genome.3. Triggering of programmed cell deatho p53 directs the transcription of several pro-apoptotic genes such as BAX and PUMA (approved name BBC3) and induces apoptosis.o It has been shown that p53 activates transcription of the mir 34 family of micro RNAs (miRNAs), mir 34a? mir34c. It has already been discussed in genetics that miRNA prevents translation of mRNA.o mir34 inhibits translation of anti-apoptotic genes such as BCL2 (there by induce apoptosis) and pro-proliferative genes such as cyclins (there by prevent proliferation) p53 induce apoptosis and prevent proliferation through mir34.
Arrest cell cycle at GI Phase
Product is 53 KD protein
Located on chromose 17
Wild/non-mutated form is associated with increased risk of child-hood tumors.