Shuttling of RecQ helicase HIM-6 coordinates iterative cycle of unwinding, pulling, and backsliding
Son Truong Le, Seung-Won Lee, Chanwoo Kim, Hajin Kim, Byungchan Ahn
TL;DR
This study reveals how the RecQ helicase HIM-6 moves along DNA and switches between unwinding and pulling activities, especially when encountering ribonucleotides.
Contribution
The study identifies a new trigger for activity switching in RecQ helicase when encountering ribonucleotides in DNA.
Findings
HIM-6's helicase domain and zinc-binding element are essential for repetitive DNA unwinding.
HIM-6 exhibits strand-pulling activity and backsliding in an iterative cycle.
Ribonucleotides in DNA cause HIM-6 to pause and switch to a pulling mode.
Abstract
RecQ DNA helicases are a highly conserved family of proteins essential for maintaining genome stability. Despite smFRET studies on repetitive DNA unwinding by RecQ using fluorophore-labeled DNA substrates, the domains controlling this behavior, direct visualization of RecQ movement, and in vivo factors such as protein partners and nucleotide modifications affecting it have remained elusive. Using fluorescently labeled HIM-6 fragments and various DNA substrates, we present the sequential functional activities of HIM-6 and its shuttling along DNA. The helicase domain and zinc-binding element together constitute a minimal functional unit responsible for repetitive unwinding, whereas larger fragments containing additional domains exhibited enhanced DNA unwinding activity and additionally acquired a new strand-pulling activity. During strand pulling, HIM-6 remains stationary and subsequently…
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Taxonomy
TopicsDNA Repair Mechanisms · RNA Research and Splicing · Microtubule and mitosis dynamics