Dear Editor,The clustered regularly interspaced short palindromic repeats-Cas(CRISPR-Cas)systems,including type II Cas9 and type V Cas12 systems,which serve in the adaptive immunity of prokaryotes against viruses,have...Dear Editor,The clustered regularly interspaced short palindromic repeats-Cas(CRISPR-Cas)systems,including type II Cas9 and type V Cas12 systems,which serve in the adaptive immunity of prokaryotes against viruses,have been developed into genome-editing tools(Anzalone et al.,2020;Doudna,2020).Compared with type II systems,the type V systems including V-A to V-K showed more functional diversity(Yan et al.,2019).Amongst them,Cas12i has a relatively smaller size(1,033-1,093 aa),compared to SpCas9 and Cas12a,and has a 5'-TTN protospacer adjacent motif(PAM)preference(Yan et al.,2019).展开更多
Dear Editor,CRISPR-Cas9 mediated seamless genome editing can be achieved by incorporating donor DNA into the CRISPR-Cas9 target loci via homology-directed repair(HDR),albeit with relative low efficiency due to the ine...Dear Editor,CRISPR-Cas9 mediated seamless genome editing can be achieved by incorporating donor DNA into the CRISPR-Cas9 target loci via homology-directed repair(HDR),albeit with relative low efficiency due to the inefficient delivery of exogenous DNA(Cox et al.,2015;Gao,2021).Retrons are bacterial phage-defense related operons composed of a specialized reverse transcriptase(RT)and a relevant non-coding RNA(ncRNA)which can be partially reverse tran-scribed by RT initiating at a conserved guanosine(G)residue to produce a multicopy single-stranded DNA(msDNA)(Yee et al.,1984;Millman et al.,2020).After being reverse transcribed,the msDNA is usually covalently teth-ered to the ncRNA through the 2',5'-phosphodiesterbond between the priming G in ncRNA and 5'end of msDNA(Dhundale et al.,1987).The reverse transcription process,of which the specialized RT recognizes the unique secondary structure of retron ncRNA,is highly specific(Hsu et al.,1989).Additionally,desired msDNA can be generated in vivo by replacing the dispensable region of retron ncRNA with desired sequences(Mirochnitchenko et al.,1994;Simon et al.,2019).Therefore,retrons are promising biological sources for in vivo generation of DNA donors for HDR-me-diated precise genome editing.展开更多
文摘Dear Editor,The clustered regularly interspaced short palindromic repeats-Cas(CRISPR-Cas)systems,including type II Cas9 and type V Cas12 systems,which serve in the adaptive immunity of prokaryotes against viruses,have been developed into genome-editing tools(Anzalone et al.,2020;Doudna,2020).Compared with type II systems,the type V systems including V-A to V-K showed more functional diversity(Yan et al.,2019).Amongst them,Cas12i has a relatively smaller size(1,033-1,093 aa),compared to SpCas9 and Cas12a,and has a 5'-TTN protospacer adjacent motif(PAM)preference(Yan et al.,2019).
文摘Dear Editor,CRISPR-Cas9 mediated seamless genome editing can be achieved by incorporating donor DNA into the CRISPR-Cas9 target loci via homology-directed repair(HDR),albeit with relative low efficiency due to the inefficient delivery of exogenous DNA(Cox et al.,2015;Gao,2021).Retrons are bacterial phage-defense related operons composed of a specialized reverse transcriptase(RT)and a relevant non-coding RNA(ncRNA)which can be partially reverse tran-scribed by RT initiating at a conserved guanosine(G)residue to produce a multicopy single-stranded DNA(msDNA)(Yee et al.,1984;Millman et al.,2020).After being reverse transcribed,the msDNA is usually covalently teth-ered to the ncRNA through the 2',5'-phosphodiesterbond between the priming G in ncRNA and 5'end of msDNA(Dhundale et al.,1987).The reverse transcription process,of which the specialized RT recognizes the unique secondary structure of retron ncRNA,is highly specific(Hsu et al.,1989).Additionally,desired msDNA can be generated in vivo by replacing the dispensable region of retron ncRNA with desired sequences(Mirochnitchenko et al.,1994;Simon et al.,2019).Therefore,retrons are promising biological sources for in vivo generation of DNA donors for HDR-me-diated precise genome editing.
