BLM解旋酶催化核心与G4DNA结合和解链特性.doc

  The binding and unwinding properties of the Bloom helicase  5 10 15 20 25 30 35 40 45 catalytic core to the G4DNA structure# LUO Heng1,2,3, XU Houqiang1, CAI Mingjuan1, CHEN Xiang1, DING Mei1, LI Kun1, MENG Huihui1** (1. Guizhou Key Laboratory of Animal Genetics and Breeding Reproduction,College of Animal Sciences,Guizhou University, GuiYang 550025; 2. Provincial Key Laboratory for Agricultural Pest Management of Mountainous Region of Guizhou University, GuiYang 550025; 3. Key Laboratory of Ministry of Education for Green Pesticide and Agrobioengineering, Guizhou University, GuiYang 550025) Abstract: G4DNA, which widely exists in the structure of the telomeres in normal cells, plays a pivotal part in the process of prolonging the telomere DNA by catalyzing the enzyme telomerase. Bloom (BLM) helicase, an important member of the RecQ DNA helicase family, plays an important role in DNA metabolism, including DNA replication, repair, transcription, and recombination. The unwinding of G4DNA requires DNA helicase participation, which is crucial for maintaining chromosomal stability. This study was conducted to determine the DNA-binding and unwinding properties of the BLM helicase catalytic core to G4DNA using fluorescence polarization and the electrophoretic mobility shift assay (EMSA). The results revealed that the BLM helicase catalytic core could bind and unwind G4DNA. The molecular affinity of G4DNA binding by the helicase was dependent on the single-stranded DNA (ssDNA) terminals in the G4DNA; the helicase binds to the G4DNA where one helicase monomer covers approximately 10 nucleotides at the 3’ or 5’ ssDNA tail. The unwinding of G4DNA was dependent on the presence of a 3’ ssDNA tail and ATP; the G4DNA with only a 3’ ssDNA tail was the most favorable substrate to be unwound by the BLM helicase catalytic core, and required 3’ ssDNA tails of at least 10 nt in length for efficient unwinding. The blunt-ended G4DNA was loosely bound and partly unwound by the helicas