Key result
Efficient RNA helicase activity of NPH-II depends exclusively on ribose moieties in the loading strand and a specific section of the 3'-overhang, though trace activity on DNA polymers can occur.
Hypothesis-generating for helicase-targeted antivirals; leaves open relevance to human cardiac RNA metabolism.
NPH-II is a prototypical member of the DExH/D subgroup of superfamily II helicases. It exhibits robust RNA helicase activity, and a detailed kinetic framework for unwinding has been established. However, like most SF2 helicases, there is little known about its mode of substrate recognition and its ability to differentiate between RNA and DNA substrates. Here, we employ a series of chimeric RNA-DNA substrates to explore the molecular determinants for NPH-II specificity on RNA and to determine if there are conditions under which DNA is a substrate. We show that efficient RNA helicase activity depends exclusively on ribose moieties in the loading strand and in a specific section of the 3'-overhang. However, we also document the presence of trace activity on DNA polymers, showing that DNA can be unwound under extremely permissive conditions that favor electrostatic binding. Thus, while polymer-specific SF2 helicases control substrate recognition through specific interactions with the loading strand, alternative specificities can arise under appropriate reaction conditions.
No takes yet. Share an insight, caveat, or question.
Jane Kawaoka (2005) studied this question. Chimeric RNA-DNA substrates was evaluated on RNA helicase activity and substrate specificity. Efficient RNA helicase activity of NPH-II depends exclusively on ribose moieties in the loading strand and a specific section of the 3'-overhang, though trace activity on DNA polymers can occur.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: