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J. Bacteriol. doi:10.1128/JB.01662-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

HJM/HEL308A DNA HELICASE FROM SULFOLOBUS TOKODAII PROMOTES REPLICATION FORK REGRESSION AND INTERACTS WITH HJC ENDONUCLEASE IN VITRO

State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, P. R. China; School of Medicine, Shandong University, Jinan, 250012, P. R. China

^* To whom correspondence should be addressed. Email: yulgshen{at}sdu.edu.cn.

	Abstract

Hjm and Hel308a are novel, RecQ-like DNA helicases recently identified in the euryarchaeotes, Pyrococcus furiosus and Methanothermobacter thermautotrophicus, respectively. In this study, an Hjm/Hel308 homologue (designated StoHjm) from Sulfolobus tokodaii, a hyperthermophilic archaeon belonging to the Crenarchaeota subdomain of archaea, was cloned, purified, and characterized. Unlike Hjm and Hel308a which unwind DNA in 3'-5' direction, StoHjm unwound DNA in both 3'-5' and 5'-3' directions. Remarkably, StoHjm exhibited structure-specific, ssDNA annealing and fork regression activities in vitro. In addition, gel filtration, affinity pull-down, and yeast two-hybrid analyses revealed that StoHjm physically interacted with StoHjc, the Holliday junction specific endonuclease from S. tokodai. This interaction may have functional significance, because the unwinding activity of StoHjm was inhibited by StoHjc in vitro. These results may suggest that the Hjm/Hel308 family helicases, in association with Hjc endonucleases, are involved in processing of stalled replication forks.