Title: The effects of low dose 60Co-gamma-radiation on radioresistance, mutagenesis, gene conversion, cell cycle and transcriptome profile in Saccharomyces cerevisiae

Authors: Meenakshi Dwivedi, Neeta Sehgal, Madhu Bala

Addresses: Division of Radiation Biology, Institute of Nuclear Medicine and Allied Sciences, Brig. S.K. Mazumdar Marg, Delhi – 110054, India. ' Department of Zoology, University of Delhi, Delhi 110 007, India. ' Division of Radiation Biology, Institute of Nuclear Medicine and Allied Sciences, Brig. S.K. Mazumdar Marg, Delhi – 110054, India

Abstract: The underlying principles of low (stress)-dose Radiation-Induced Radioresistance (RIR) are inadequately understood. The present investigation focuses on understanding the genetic basis of RIR in Saccharomyces cerevisiae. In comparison with non-pre-irradiated cultures, the cultures that were pre-irradiated with a low dose of 60Co γ-radiation showed increased survivors (32%) but decreased convertants (26%) and revertants (65%) after irradiation with a lethal dose of 60Co γ-radiation. The radioresistance was higher if the stress dose was delivered at lower dose rate. The prolonged S-phase upregulation of genes from clusters of signal transduction, DNA damage repair, stress response, cell cycle and energy generation and down-regulation of genes from Unfolded Protein Response (UPR) pathways were observed in stress-dose irradiated cells when studied with the microarray technique. The post-irradiation variations in Heat Shock Proteins (HSPs) and the Mre11-Rad50-Xrs2 (MRX) complex were time-dependent and confirmed by real-time Quantitative-Polymerase Chain Reaction (Q-PCR) and Western blotting. This study suggests a combined role of HSPs and the MRX complex in RIR.

Keywords: 60Co-gamma radiation; low dose radiation; gene convertants; heat shock proteins; HSPs; microarray; MRX complex; rdiation-induced radioresistance; mutagenesis; low radiation; gene conversion; cell cycle; transcriptome profile; Saccharomyces cerevisiae.

DOI: 10.1504/IJLR.2008.020978

International Journal of Low Radiation, 2008 Vol.5 No.4, pp.290 - 309

Available online: 29 Oct 2008 *

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