DNA2 in Chromosome Stability and Cell Survival—Is It All about Replication Forks?

Abstract

The conserved nuclease-helicase DNA2 has been linked to mitochondrial myopathy, Seckel syndrome, and cancer. Across species, the protein is indispensable for cell proliferation. On the molecular level, DNA2 has been implicated in DNA double-strand break (DSB) repair, checkpoint activation, Okazaki fragment processing (OFP), and telomere homeostasis. More recently, a critical contribution of DNA2 to the replication stress response and recovery of stalled DNA replication forks (RFs) has emerged. Here, we review the available functional and phenotypic data and propose that the major cellular defects associated with DNA2 dysfunction, and the links that exist with human disease, can be rationalized through the fundamental importance of DNA2-dependent RF recovery to genome duplication. Being a crucial player at stalled RFs, DNA2 is a promising target for anti-cancer therapy aimed at eliminating cancer cells by replication-stress overload.

Decoding Cancer Variants of Unknown Significance for Helicase–Nuclease–RPA Complexes Orchestrating DNA Repair During Transcription and Replication

“…DNA2 is a structure-specific 5′–3′ nuclease/helicase that contains a PD-(D/E)XK superfamily nuclease motif resembling EXO5 plus a superfamily 1 (SF1) helicase domain ( Figure 8A ). DNA2 acts in DNA double-strand break repair ( Zhu et al, 2008 ), Okazaki fragment maturation ( Bae et al, 2001 ), and stalled replication fork restart ( Hudson and Rass, 2021 ; Thangavel et al, 2015 ; Zheng et al, 2020 ). The nuclease and helicase domains are connected by a β-barrel domain with a stalk of two long α-helices to form a DNA binding tunnel for threading ( Figure 8B ; Supplementary Video S6 ).…”

Rothmund-Thomson syndrome, a disorder far from solved

“…During lagging strand replication, the yeast Pif1 helicase, together with the Polδ (delta) subunit, Pol32, unwind previously synthesized Okazaki fragments. If these fragments are short (<30 nt), they are readily cleaved by the canonical flap endonuclease FEN1 (Kang et al, 2010;Hudson and Rass, 2021). However, if longer flaps (>30 nt) are generated, these are covered by RPA, inhibiting the action of Fen1 and requiring DNA2 to incise the flap and remove a large portion of the ssDNA region, allowing Fen1 to process the resulting short flap (Bae and Seo, 2000;Bae et al, 2001;Rossi et al, 2018;Kahli et al, 2019).…”

“…DNA2 is also important during replication fork reversal (Neelsen and Lopes, 2015;Hudson and Rass, 2021), which is a process by which DNA replication forks are remodeled to allow their restart after their progression has been blocked (Zellweger et al, 2015). DNA2 is recruited to stalled replication forks and is required for controlled nucleolytic degradation of reversed replication forks, in concert with WRN, which promotes replication restart and prevents the aberrant processing of replication intermediates by other pathways (Hu et al, 2012;Neelsen and Lopes, 2015;Thangavel et al, 2015;Hudson and Rass, 2021).…”

USP50 suppresses alternative RecQ helicase use and deleterious DNA2 activity during replication

“…The human nuclease-helicase DNA2 recently emerged as critical to stalled replication fork processing (reviewed in 29 ), where it alleviates replication stress by promoting resection 30 . DNA2 functions with BLM and WRN helicases in DNA end resection 31, 32 , but its role in replicative stress is linked to WRN, where DNA2:WRN degrade reversed forks to promote restart 22 .…”