论文部分内容阅读
Dear Editor,rnPrecise and efficient genome editing is very important for gene functional characterization.In recent years,sequence-specific DNA nucleases have been developed to increase the efficiency of gene targeting or genome editing in animals and plants.Among them,Zinc-Finger Nucleases (ZFNs) and Transcription Activator-Like Effector Nucleases (TALENs) are two most commonly used sequencespecific chimeric proteins (Gaj et al.,2013).Recently,a breakthrough gene-targeting tool based on RNA-guided Cas9 nuclease from type Ⅱ prokaryotic Cluster Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated system has been developed (Jinek et al.,2012).CRISPR/Cas system is an adaptive defense system in prokaryotes to fight against alien nucleic acids (Horvath and Barrangou,2010).The CRISPR loci are variable short spacers separated by short repeats,which are transcribed into synthetic single-guide RNA (sgRNA).The sgRNA forms a functional complex with CRISPR-associated nuclease (Cas9) and guide the nuclease to genomic loci matching a 20-bp complementary invading DNA,cleaving it immediately upstream of a required 5’-NGG Protospacer Adjacent Motif (PAM).A chimeric sgRNA that mimics the natural synthetic sgRNA can be used to target Cas9 for genome editing in eukaryotic cells.