Heliscreener(TM) WRN Helicase Unwinding Assay

The Heliscreener WRN Helicase DNA Unwinding Assay is a biochemical assay designed to measure the DNA unwinding activity of BLM helicase (BLM-H). The assay utilizes a labeled double-stranded DNA substrate that is quenched when intact and emits far-red fluorescence following unwinding. The assay can be performed in kinetic (continuous monitoring) or endpoint mode. Kinetic mode is recommended for initial velocity measurements, allowing for accurate enzyme kinetics and inhibitor IC50 determinations. Alternatively, for screening, the enzyme reaction can be stopped by adding the Stop & Detect Buffer B, and the quenched reactions can be read in endpoint mode. Protein Function: Multifunctional enzyme that has magnesium and ATP-dependent 3'-5' DNA-helicase activity on partially duplex substrates (PubMed:9224595, PubMed:9288107, PubMed:9611231). Also has 3'->5' exonuclease activity towards double-stranded (ds)DNA with a 5'-overhang (PubMed:11863428). Has no nuclease activity towards single-stranded (ss)DNA or blunt-ended dsDNA (PubMed:11863428). Helicase activity is most efficient with (d)ATP, but (d)CTP will substitute with reduced efficiency, strand displacement is enhanced by single-strand binding-protein (heterotrimeric replication protein A complex, RPA1, RPA2, RPA3) (PubMed:9611231). Binds preferentially to DNA substrates containing alternate secondary structures, such as replication forks and Holliday junctions. May play an important role in the dissociation of joint DNA molecules that can arise as products of homologous recombination, at stalled replication forks or during DNA repair. Alleviates stalling of DNA polymerases at the site of DNA lesions. Plays a role in the formation of DNA replication focal centers, stably associates with foci elements generating binding sites for RP-A (By similarity). Plays a role in double-strand break repair after gamma-irradiation (PubMed:9224595, PubMed:9288107, PubMed:9611231). Unwinds some G-quadruplex DNA (d(CGG)n tracts), unwinding seems to occur in both 5'-3' and 3'-5' direction and requires a short single-stranded tail (PubMed:10212265). d(CGG)n tracts have a propensity to assemble into tetraplex structures, other G-rich substrates from a telomeric or IgG switch sequence are not unwound (PubMed:10212265). Depletion leads to chromosomal breaks and genome instability (PubMed:33199508) [The Uniprot Consortium]