Bioinformatic analysis of RecQ4 helicases reveals the presence of a RQC domain and a Zn knuckle

- The similarity between yeast Sld2 and the N-terminal region of RecQ4 extends to the entire Sld2 sequence.
- The N-terminal domain of RecQ4 contains a Zn knuckle.
- A putative RQC domain can be identified in RecQ4, including a Zn domain and a winged helix domain.

RecQ helicases play essential roles in the maintenance of genome stability and contain a highly conserved helicase region generally followed by a characteristic RecQ-C-terminal (RQC) domain, plus a number of variable associated domains. Notable exceptions are the RecQ4 helicases, where none of these additional regions have been described. Particularly striking was the fact that no RQC domain had been reported, considering that the RQC domain had been shown to play an essential role in the catalytic mechanism of most RecQ family members. Here we present the results of detailed bioinformatic analyses of RecQ4 proteins that identify, for the first time, the presence of a putative RQC domain, including some of the key residues involved in DNA binding and unwinding. We also describe the presence of a novel “Zn knuckle” domain, as well as an additional Sld2-homology region, providing new insights into the architecture, function and evolution of these enzymes.