Fe-S family helicases, including FANCJ, DDX11/ChlR1, xeroderma pigmentosum complementation group D (XPD), and regulator of telomere elongation helicase 1 (RTEL1), are closely related to G4 function modulation (White, 2009; Guo et al., 2015; Estep and Brosh, 2018). The gene discussed is RTEL1; the disease is Xeroderma pigmentosum complementation group D.