Eminyakeni eyishumi edlule, ubuchwepheshe bokuhlela izakhi zofuzo obusekelwe ku-CRISPR buye bathuthuka ngokushesha, futhi busetshenziswe ngempumelelo ekwelapheni izifo zofuzo kanye nomdlavuza ekuhlolweni kwemitholampilo yabantu.Ngaso leso sikhathi, ososayensi emhlabeni wonke bahlala bethepha amathuluzi amasha anamandla okuhlela isakhi sofuzo ukuze axazulule izinkinga zamathuluzi akhona okuhlela izakhi zofuzo nezinqumo.

NgoSepthemba 2021, ithimba likaZhang Feng lashicilela iphepha kujenali yeSayensi [1], futhi lathola ukuthi inqwaba yama-transposter anekhodi ye-RNA eqondisa ama-nucleic acid enzymes futhi ayiqamba ngokuthi i-Omega system (okubandakanya i-ISCB, ISRB, TNP8).Ucwaningo luphinde lwathola ukuthi uhlelo lwe-Omega lusebenzisa ingxenye ye-RNA ukuze iqondise iketango elikabili le-DNA elisikwayo, okuyi-ωRNA.Okubaluleke nakakhulu, lawa ma-enzyme e-nucleic acid mancane kakhulu, cishe amaphesenti angama-30 kuphela e-CAS9, okusho ukuthi kungenzeka ukuthi alethwe kumaseli.

Ngo-Okthoba 12, 2022, ithimba likaZhang Feng lanyathelisa kujenali yezeMvelo enesihloko esithi: Structure of the Omega Nickase ISRB in Complex with ωrna and Target DNA [2].

Ucwaningo luqhubekile lwahlaziya ukwakheka kwesibonakhulu se-electron eqandisiwe se-ISRB-ωRNA kanye nenkimbinkimbi ye-DNA eqondiwe ohlelweni lwe-Omega.

I-ISCB ingukhokho we-CAS9, futhi i-ISRB yinto efanayo yokuntuleka kwesizinda se-HNH nucleic acid se-ISCB, ngakho usayizi mncane, cishe ama-amino acid angama-350 kuphela.I-DNA iphinde inikeze isisekelo sentuthuko eyengeziwe kanye noshintsho lobunjiniyela.

I-IsrB eqondiswa yi-RNA iyilungu lomndeni we-OMEGA efakwe ikhodi yomndeni omkhulu we-IS200/IS605 wama-transposon.Kusukela ekuhlaziyweni kwe-phylogenetic kanye nezizinda eziyingqayizivele ezabiwe, i-IsrB cishe izoba ngumanduleli we-IscB, ongukhokho we-Cas9.

NgoMeyi 2022, i-Lovely Dragon Laboratory yaseCornell University yashicilela iphepha kumagazini iSayensi [3], ihlaziya ukwakheka kwe-IscB-ωRNA kanye nendlela yayo yokusika i-DNA.

Uma kuqhathaniswa ne-IscB ne-Cas9, i-IsrB ayinayo isizinda se-nuclease se-HNH, i-REC lobe, kanye nezizinda eziningi ezilandelanayo ze-PAM, ngakho i-IsrB incane kakhulu kune-Cas9 (kuphela mayelana ne-350 amino acids).Kodwa-ke, usayizi omncane we-IsrB ulinganiswa ngomhlahlandlela omkhulu we-RNA (i-omega RNA yayo icishe ibe ngamasentimitha angama-300 ubude).

Ithimba lika-Zhang Feng lihlaziye ukwakheka kwesibonakhulu se-cryo-electron se-IsrB (DtIsrB) lisuka kubhaktheriya enomswakama wokushisa i-Desulfovirgula thermocuniculi kanye nenkimbinkimbi ye-ωRNA kanye ne-DNA eqondiwe.Ukuhlaziywa kwesakhiwo kubonise ukuthi ukwakheka okuphelele kweprotheni ye-IsrB kwabelane ngesakhiwo somgogodla ne-Cas9 protein.

Kodwa umehluko ukuthi i-Cas9 isebenzisa i-REC lobe ukwenza lula ukuqashelwa okuqondiwe, kuyilapho i-IsrB ithembele ku-ωRNA yayo, ingxenye yayo eyenza uhlaka oluyinkimbinkimbi lwezinhlangothi ezintathu olusebenza njenge-REC.

Ukuze uqonde kangcono izinguquko zesakhiwo se-IsrB ne-Cas9 ngesikhathi sokuvela kwe-RuvC, ithimba lika-Zhang Feng laqhathanisa izakhiwo ezibophezela i-DNA ezihlosiwe ze-RuvC (TtRuvC), IsrB, CjCas9 kanye ne-SpCas9 kusukela ku-Thermus thermophilus.

Ukuhlaziywa kwesakhiwo se-IsrB kanye ne-ωRNA yayo kucacisa ukuthi i-IsrB-ωRNA ibona ngokuhlanganyela futhi iyihlukanise kanjani i-DNA ehlosiwe, futhi inikeza isisekelo sokuthuthuka nobunjiniyela bale nuclease encane.Ukuqhathaniswa namanye amasistimu aqondiswa yi-RNA kugqamisa ukusebenzisana okusebenzayo phakathi kwamaprotheni nama-RNA, kuthuthukiswe ukuqonda kwethu ngebhayoloji kanye nokuvela kwalezi zinhlelo ezihlukahlukene.

Izixhumanisi:

1.https://www.science.org/doi/10.1126/science.abj6856

2.https://www.science.org/doi/10.1126/science.abq7220

3.https://www.nature.com/articles/s41586-022-05324-6