CRISPR cas enzyme series gene edit virus detection

Cas9 nuclease from S. pyogenes is RNA mediated endonuclease, which can specifically cut double stranded DNA (in the presence of DNA PAM, it can also cut single stranded DNA or single stranded RNA). The Cas9 cutting site is located in the target sequence, 3 bases away from the PAM (NGG) region. PAM is necessary for Cas9 identification and cutting. Because the reaction requires the addition of RNA (sgRNA or crRNA: tracrRNA), the whole system, including Cas9 enzyme, must not contain any nuclease activity.

Cas12a nuclease (formerly known as Cpf1) is an RNA mediated endonuclease that can specifically cleave target double stranded DNA in the presence of PAM. Different from Cas9: (1) Cas12a only needs a single crRNA, and it is smaller and easier to be delivered to cells; (2) After cutting Cas12a, sticky ends are generated, which is more conducive to precise genome editing; (3) The cutting site of Cas12a is far away from its recognition site, which provides the possibility of continuous multiple edits; (4) The PAM sequence recognized by Cas12a is different from that of Cas9, so it provides a choice of different editing sites; For different Cas12a proteins, the PAM sites required for target recognition are different. Some Cas12a proteins recognize TTN sites and some Cas12a proteins recognize TTTN sites. This product (including Cas12a enzyme) does not contain any nuclease activity other than Cas12a.