Question

help me with that please this question is cery important i have a final ,

7. Loss-of-function mutations in p53 typify the ajority of human cancers Discovery of the roles for p53 in the DNA damage checkpoint and in apoptosis helps to explain its potency as a tumor suppressor protein. Recent studies suggest that p53 may possess an additional anti-tumor function: preventing telomerase activity. In one such study by Ogawa and colleagues, a human pancreatic cell line called MIA PaCa-2, which lacks functional p53, was infected with replication-defective adenoviruses encoding p53, p21 or a control protein (lacZ), Western blot analysis of these cells for p21 and p53 is shown below Why do cells infected with adenovirus encoding p53 (Ad-p53) also express p21? Why do uninfected cells fail to express endogenous p21? Control and adenovirus-infected MIA PaCa-2 cells were then tested for telomerase activity. The results of the assay are shown in the table below. a. Pre-treatment uninfected Ad-lacz Ad-p21 Ad-p53 Telomerase -Activity (%) 97 100 100 What is the significance of telomerase activity in the pretreatment and uninfected MIA PaCa-2 cells? How does telomerase contribute to the b. malignant phenotype?

Answer 1

7) a) The diagram explaining the action of p53 and p21 with cell regulation is shown below as follows namely like:

Cell Cycle Arrest Triptolide ASPP c-Jun E1A Deacetylase inhibitors TGFB inhibitors → Spl/Sp3 DNA-damage p21 _- NF-kB Oxidative stress FNY IL-3 IL-6 Apoptosis

The effect of p53 activation takes place after observing a DNA damage response with oxidative stress in the cell. p53 activates p21 which causes the activation of p21 which causes the cell cycle arrest in the cell. The uninfected cells have defective p53 which does not activate the p21 protein inside the cell. p53 has a role in telomere protection as it is evident in the studies of transfection of replication defective p53 and p21 adeno virus constructs in pancreatic cell line MIA PaCa-2. There is reduction in the activity of this cell line after transfection with p53 adeno virus replication defective construct in the cell line MIA PaCa-2. There are non canonical p53 response elements present in the subtelomeric regions of the chromosomes. This mechanism causes the activation of the histone acetylation proteins leading to the process of prevention of accumulation of $\gamma$H2AX protein. This mechanism stabilizes the telomere tract. There is binding of telomere binding factor-2 on the telomeric region of the DNA. This mechanism is shown below in the form of a diagram as shown like:

Normal Telomere T-loop TRE2XTRF TRF1(TIN2 RF2XTRF1 RF RF TRF2 RF1 XTRF2 TRF1 RF1XTRF DNA Damage PARD6G (subtelomeric RNA) Ac p53-Mediated Telomere Protection Pol II TERR eRNA Ac p53 Pol II RF2 RF2 Ac RF1 N2 RF2 RF1 RF1XTRF2XTRF1 RFI ot

c) Cells infected with p21 replication defective construct provides evidence that there is continuation of the telomerase activity in the pancreatic cell line as the p53 protein present in these cells is inherently defective and does not cause the activation of the telomere stabilization activity and histone acetylation pathway.

d) and e) p53 inhibits the process of apoptosis and this activity is inhibited by the activation of human telomerase catalytic subunit inside the cells which can be explained by the analysis of genes by the process of reverse transcriptase-PCR.This further initiates the process of resistance to DNA damage response inside the cell lines and deactivation of the p53 signaling pathway inside the cell line. There is activation of human fibroblast growth factor which causes the inhibition of the p53 activation response of prevention of apoptosis inside the cell line.