# Helicase HELQ: Molecular Characters Fit for DSB Repair Function

## TL;DR

This paper reviews how the DNA helicase HELQ contributes to repairing DNA double-strand breaks through various biochemical functions.

## Contribution

The paper highlights HELQ's strand-annealing activity and its role in multiple DSB repair pathways.

## Key findings

- HELQ supports end resection and downstream steps in DSB repair pathways like HR and MMEJ.
- HELQ's biochemical functions are conserved from archaea to humans and are essential for DNA repair.
- The enzyme plays a role in strand invasion, DNA synthesis, and gene conversion during repair.

## Abstract

The protein sequence and spatial structure of DNA helicase HELQ are highly conserved, spanning from archaea to humans. Aside from its helicase activity, which is based on DNA binding and translocation, it has also been recently reconfirmed that human HELQ possesses DNA–strand–annealing activity, similar to that of the archaeal HELQ homolog StoHjm. These biochemical functions play an important role in regulating various double–strand break (DSB) repair pathways, as well as multiple steps in different DSB repair processes. HELQ primarily facilitates repair in end–resection–dependent DSB repair pathways, such as homologous recombination (HR), single–strand annealing (SSA), microhomology–mediated end joining (MMEJ), as well as the sub-pathways’ synthesis–dependent strand annealing (SDSA) and break–induced replication (BIR) within HR. The biochemical functions of HELQ are significant in end resection and its downstream pathways, such as strand invasion, DNA synthesis, and gene conversion. Different biochemical activities are required to support DSB repair at various stages. This review focuses on the functional studies of the biochemical roles of HELQ during different stages of diverse DSB repair pathways.