Involvement of Human Small Fragment Nuclease in the Resistance of Human Cells to UV-C–induced Cell Death

• Published in: Photochemistry and photobiology 2004-09, Vol.80 (2), p.281-285
• Main Authors: Ito, Seiro, Kita, Kazuko, Zhai, Ling, Wano, Chieko, Suzuki, Toshikazu, Yamaura, Akira, Suzuki, Nobuo
• Format: Article
• Language: English
• Subjects: 14-3-3 Proteins; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Caspase 3; Caspases - metabolism; Cell death; Cell Death - drug effects; Cell Death - radiation effects; Cell Line; Exonucleases - genetics; Exonucleases - metabolism; Exoribonucleases; Humans; Kinetics; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Pyrimidine Dimers - metabolism; Research s; RNA Interference; RNA, Messenger - genetics; RNA, Messenger - metabolism; Ultraviolet Rays
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1562/2004-01-21-RA-051.1

Human small fragment nuclease (Sfn) is one of the cellular proteins that were reported to degrade small, single-stranded DNA and RNA. However, the biological role of Sfn in cellular response to various stressors such as UV-C (mainly 254 nm wavelength ultraviolet ray) remains unclear. We have examined whether modulation of human SFN gene expression affects cell survival capacity against UV-C–induced cell death, analyzing colony survival ability in UV-C–sensitive human RSa cells treated with short double-stranded RNA (siRNA) specific for SFN messenger RNA (mRNA). The expression levels of SFN mRNA in the siRNA-treated RSa cells decreased to about 15% compared with those in the control siRNA-treated cells. The siRNA-treated RSa cells showed lower colony survival and higher activity of caspase-3 after UV-C irradiation than the control siRNA-treated RSa cells. Furthermore, the removal capacity of cyclobutane pyrimidine dimers (CPD) in the siRNA-treated RSa cells decreased compared with the control siRNA-treated RSa cells. There was no difference in the colony survival and CPD removal capacity after UV-C irradiation between the control siRNA-treated RSa cells and mock-treated RSa cells. These results suggest that SFN expression is involved in resistance of RSa cells to UV-C–induced cell death through the roles it plays in the DNA repair process.