Insights into the Activities of Helicases from Thermococcales: The Cases of the RNA Helicase ASH-Ski2, the DNA Helicase Hel308, and the RNA:DNA Helicase Lhr2.

Helicases are versatile enzymes. Superfamily 2 (SF2) is the largest and most diverse group of helicases. SF2 helicases are involved in fundamental processes dealing with nucleic acids in the three domains of life and can be specific to DNA, RNA, or DNA:RNA hybrids. They are known to catalyze unwinding reactions in vitro or disrupt duplexes in vivo. More recently, it has emerged that they can also anneal single strands to form duplexes. Here, we describe biochemical assays used to investigate the activities of the Ski2-like helicases ASH-Ski2 and Hel308, as well as the Lhr-like helicase Lhr2 from Thermococcales, an order of hyperthermophilic archaea. Unwinding and strand-annealing assays using a range of substrates revealed that they are RNA-, DNA-, or RNA:DNA-specific helicases, respectively.