Functional conservation of RecQ helicase BLM between humans and Drosophila melanogaster.

RecQ helicases are a family of proteins involved in maintaining genome integrity with functions in DNA repair, recombination, and replication. The human RecQ helicase family consists of five helicases: BLM, WRN, RECQL, RECQL4, and RECQL5. Inherited mutations in RecQ helicases result in Bloom Syndrome (BLM mutation), Werner Syndrome (WRN mutation), Rothmund-Thomson Syndrome (RECQL4 mutation), and other genetic diseases, including cancer. The RecQ helicase family is evolutionarily conserved, as Drosophila melanogaster have three family members: DmBlm, DmRecQL4, and DmRecQL5 and DmWRNexo, which contains a conserved exonuclease domain. DmBlm has functional similarities to human BLM (hBLM) as mutants demonstrate increased sensitivity to ionizing radiation (IR) and a decrease in DNA double-strand break (DSB) repair. To determine the extent of functional conservation of RecQ helicases, hBLM was expressed in Drosophila using the GAL4 > UASp system to determine if GAL4 > UASp::hBLM can rescue DmBlm mutant sensitivity to IR. hBLM was able to rescue female DmBlm mutant sensitivity to IR, supporting functional conservation. This functional conservation is specific to BLM, as human GAL4 > UASp::RECQL was not able to rescue DmBlm mutant sensitivity to IR. These results demonstrate the conserved role of BLM in maintaining the genome while reinforcing the applicability of using Drosophila as a model system to study Bloom Syndrome.