Title Novel nuclear targeting coiled-coil protein of Helicobacter pylori showing Ca2+-independent, Mg2+-dependent DNase I activity
Author Young Chul Kwon1, Sinil Kim2, Yong Seok Lee3, Je Chul Lee4, Myung-Je Cho1, Woo-Kon Lee1, Hyung-Lyun Kang1, Jae-Young Song1, Seung Chul Baik1, and Hyeon Su Ro2*
Address 1Department of Microbiology, Gyeongsang National University School of Medicine, Jinju 52727, Republic of Korea, 2Division of Life Science and Research Institute of Life Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea, 3Department of Life Science and Biotechnology, Soonchunhyang University, Asan 31538, Republic of Korea, 4Department of Microbiology, Kyungpook National University School of Medicine, Daegu 41944, Republic of Korea
Bibliography Journal of Microbiology, 54(5),387-395, 2016,
DOI 10.1007/s12275-016-5631-9
Key Words coiled-coil, DNase I, Helicobacter pylori, HP0059
Abstract HP0059, an uncharacterized gene of Helicobacter pylori, encodes a 284-aa-long protein containing a nuclear localization sequence (NLS) and multiple leucine-rich heptad repeats. Effects of HP0059 proteins in human stomach cells were assessed by incubation of recombinant HP0059 proteins with the AGS human gastric carcinoma cell line. Wild-type HP0059 proteins showed cytotoxicity in AGS cells in a concentrationdependent manner, whereas NLS mutant protein showed no effect, suggesting that the cytotoxicity is attributed to host nuclear localization. AGS cells transfected with pEGFP-HP0059 plasmid showed strong GFP signal merged to the chromosomal DNA region. The chromosome was fragmented into multiple distinct dots merged with the GFP signal after 12 h of incubation. The chromosome fragmentation was further explored by incubation of AGS chromosomal DNA with recombinant HP0059 proteins, which leaded to complete degradation of the chromosomal DNA. HP0059 protein also degraded circular plasmid DNA without consensus, being an indication of DNase I activity. The DNase was activated by MgCl2, but not by CaCl2. The activity was completely blocked by EDTA. The optimal pH and temperature for DNase activity were 7.0–8.0 and 55°C, respectively. These results indicate that HP0059 possesses a novel DNase I activity along with a role in the genomic instability of human gastric cells, which may result in the transformation of gastric cells.