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LIFE01200604005 Shri Somnath Ghosh - Homi Bhabha National ...

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CHAPTER 3<br />

RESULTS<br />

y<br />

Relative expression of DNA-PK<br />

30000<br />

25000<br />

20000<br />

15000<br />

10000<br />

5000<br />

0<br />

2h+Act 2h+Act+In 4h+Act 4h+Act+In 6h+Act 6h+Act+In 8h+Act 8h+Act+In<br />

Time (h) 2 2 4 4 6 6 8 8<br />

Actinomycin (5mg/ml) + + + + + + + +<br />

p38 MAPK inhibitor (1µM) - + - + - + - +<br />

DNA-PK<br />

Fig.3.1.9 Stabilization of DNA-PK mRNA in A549, that had been exposed to 2 Gy of 60 Co γ-<br />

irradiation daily over a period of 5 days and its stabilization is control by p38 MAP Kinase.<br />

3.1.10 Role of Rad52 and MLH1<br />

Since there was an intense activation of Rad52 and MLH1 in A549 cells exposed to fractionated<br />

irradiation, it was of interest to look for their role in survival of A549 cells. MLH1 and Rad52<br />

gene expression knockdown was carried out in A549 cells using MLH1 and Rad52 shRNA<br />

plasmids. Stably transfected cells were selected and the transfection efficiency was found to be<br />

85% for MLH1 gene and 80% for Rad52 gene.<br />

There was 48±2.8% survival of A549 cells exposed to fractionated irradiation. The survival of<br />

A549 cells that had been transfected with MLH1 shRNA plasmid and exposed to fractionated<br />

irradiation was found to be 40±1.8% where as the survival of A549 cells that had been<br />

transfected with Rad52 shRNA plasmid and exposed to fractionated irradiation was found to be<br />

136

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