Hjm/Hel308A DNA helicase from Sulfolobus tokodaii promotes replication fork regression and interacts with Hjc endonuclease in vitro.
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 a 3'-to-5' direction, StoHjm unwound DNA in both 3'-to-5' and 5'-to-3' directions. Remarkably, StoHjm exhibited structure-specific single-stranded-DNA-annealing and fork regression activities in vitro. In addition, gel filtration, affinity pulldown, and yeast two-hybrid analyses revealed that StoHjm physically interacted with StoHjc, the Holliday junction-specific endonuclease from S. tokodaii. 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.
Li
Zhuo
Z
State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China.
Lu
Shuhong
S
Hou
Guihua
G
Ma
Xiaoqing
X
Sheng
Duohong
D
Ni
Jinfeng
J
Shen
Yulong
Y
D019843:Archaeal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D019641:DNA, Archaeal / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004720:Endonucleases / Q000378:metabolism*; D011485:Protein Binding; D016944:Sulfolobus / Q000201:enzymology*; D020798:Two-Hybrid System Techniques
D019843:Archaeal Proteins; D019641:DNA, Archaeal; D004277:DNA, Single-Stranded; D004720:Endonucleases; D004265:DNA Helicases