Functional conservation of RecQ helicase BLM between humans and Drosophila melanogaster

Rebecca L. Cox,Romil K. Patel,Yaron Dayani,Carolyn M. Hofley,Jeannine R. LaRocque,Madison Betcher,Pallavi Tatapudy

doi:10.1038/s41598-019-54101-5

Rebecca L. Cox, Romil K. Patel + Show 5 more

Open Access

https://doi.org/10.1038/s41598-019-54101-5

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Abstract

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.

Highlights

One of the fundamental biological processes of the cell is to transmit genetic information to its daughter cells efficiently and accurately
BLM is involved in several aspects of the double-strand break (DSB) repair pathway called homologous recombination (HR) including 5′ to 3′ end resection[10,11], branch migration of the D loop[12], and dissolution
One of the benefits of the Galactose responsive transcription factor 4 (GAL4) > UAS system is the ability to express a gene of interest both spatially and temporally, depending on the GAL4 driver as well as the UAS sequence associated with a gene of interest[25]

Summary

Introduction

One of the fundamental biological processes of the cell is to transmit genetic information to its daughter cells efficiently and accurately. There are multiple types of DNA damage, including inter and intrastrand crosslinks, base-pair mutations, and single- and double-strand breaks (DSBs)[1]. Mutations in BLM result in chromatid gaps and breaks, chromosome rearrangements, and an increase in sister chromatid exchanges[16,17] These characteristics and deficiencies seen in BS patients and cells demonstrate chromosome instability, which may be reflected in hypersensitivity to DNA-damaging agents. The two BLM orthologs share similar protein domains (Fig. 1), consensus in the RecQ helicase domain (Supplementary Fig. S2A)[23], and 30% identity and 47% similarity across the entire protein sequence[24] These observations prompted us to investigate the extent of functional conservation of BLM between these humans and Drosophila. The ability of BLM to repair IR-induced DSBs was tested by examining the sensitivity of DmBlm mutants to IR in the presence of hBLM

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Conclusion