R环的形成及对基因组稳定性的影响.pdf

R-loop structure: the formation and the effects on genomic stability
Xuefeng Pan1,2, Nan Jiang1, Xifang Chen1, Xiaohong Zhou1, Liang Ding2, Fei Duan2
1. School of Life Science, Beijing Institute of Technology, Beijing 100081, China;
2. School of Basic Medicine, Hebei University, Baoding 071002, China
Abstract: R-loop is a type of three-stranded nucleic acid structure that is made up of an RNA:DNA hybrid, formed
due to failing separation of a nascent RNA molecule with transcripting template in transcription or by the
re-annealing of RNA molecule with one of the two strands in a double stranded DNA molecule, along with the single
stranded DNA, which is either the non-template strand in the transcription bubble or the RNA substituted DNA strand.
Formation of R-loops can occur when transcription goes through a genomic DNA region having a tract of G bases in
the non-template strand in the transcription bubble or through a type of triplet microsatellite DNA sequences that are
known to be associated with certain human diseases. The negative supercoiling forces accumulated in the transcription
bubble, and the misprocessing of RNA precursors, as well as the delayed utilizations and transportations of RNA
molecules to cytoplasm promote R loop formation. Many studies show that cells can manage R loop formation with
efficiency, and can also process the R-loops already formed in the cell, and by which, the bad effects of R-loops on  DNA replication, gene mutation and homologous recombination can be regulated, This review summarizes the formation
and the impacts of R-loops on DNA replication, mutation rates and the frequencies of homologous recombination,
and also discusses the possible role of the R-loop induced DNA replication in mediating trinucleotide repeat
expansions as seen with those frequently associatedwith human neuromuscular degenerative diseases.
Keywords: RNA:DNA hybrid; R-loop; gene transcription; DNA replication; genome stability

(最近的一篇文章）绝对不是应用学科