Cas9 variants and methods of use thereof
The present disclosure provides variant Cas9 proteins, nucleic acids encoding the variant Cas9 proteins, and host cells comprising the nucleic acids. The present disclosure provides systems that include a subject variant Cas9 protein (and/or a nucleic acid encoding the variant Cas9 protein) and a Cas9 guide RNA. In some cases, a subject system includes a PAMmer and/or a donor polynucleotide. The variant Cas9 proteins and the nucleic acids encoding the variant Cas9 proteins are useful in a wide variety of methods, which are also provided. In some embodiments, a variant Cas9 protein includes a RuvC domain, an HNH domain, and a disrupted RuvC/HNH linker region that reduces the RuvC cleavage activity of the protein. In some embodiments, a variant Cas9 protein includes a deletion (of all or a part of the HNH domain) or an insertion (within the HNH domain) that reduces the HNH cleavage activity of the protein.
1. A nucleic acid comprising a nucleotide sequence encoding a variant Cas9 protein with reduced HNH cleavage activity relative to a corresponding wild type Cas9 protein, wherein the variant Cas9 protein comprises:
(a) a RuvC domain, and
(b) at least one of:
(i) a deletion of 100 or more amino acids within the HNH domain that reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein, and
(ii) an insertion, within the HNH domain, of a heterologous amino acid sequence that provides a heterologous activity to the variant Cas9 protein relative to the corresponding wild type Cas9 protein, wherein said insertion reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein.
2. The nucleic acid of claim 1 , wherein the variant Cas9 protein comprises a deletion of 150 or more amino acids within the HNH domain that reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein.
3. The nucleic acid of claim 1 , wherein the nucleotide sequence encoding the variant Cas9 protein is operably linked to a transcription control sequence.
4. The nucleic acid of claim 3 , wherein the transcription control sequence is a promoter that is operable in a eukaryotic cell.
5. The nucleic acid of claim 1 , wherein the nucleic acid is a recombinant expression vector.
6. The nucleic acid of claim 5 , wherein the recombinant expression vector is a viral vector.
7. A cell comprising the nucleic acid of claim 1 .
8. The cell of claim 7 , wherein the cell is a eukaryotic cell.
9. A system comprising:
A) a variant Cas9 protein with reduced HNH cleavage activity relative to a corresponding wild type Cas9 protein, or a nucleic acid comprising a nucleotide sequence encoding the variant Cas9 protein, wherein the variant Cas9 protein comprises:
(a) a RuvC domain, and
(b) at least one of:
(i) a deletion of 100 or more amino acids within the HNH domain that reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein, and
(ii) an insertion, within the HNH domain, of a heterologous amino acid sequence that provides a heterologous activity to the variant Cas9 protein relative to the corresponding wild type Cas9 protein, wherein said insertion reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein; and
B) a Cas9 guide RNA, or one or more nucleic acids encoding a Cas9 guide RNA.
10. The system of claim 9 , wherein the variant Cas9 protein comprises a deletion of 150 or more amino acids within the HNH domain that reduces the HNH cleavage activity of the variant Cas9 protein relative to the HNH cleavage activity of the corresponding wild type Cas9 protein.
11. The system of claim 9 , comprising a PAMmer.
12. The system of claim 9 , comprising a donor polynucleotide.
13. A method of binding a target nucleic acid, comprising:
contacting a target nucleic acid with the system of claim 9 , wherein the Cas9 guide RNA forms a complex with the variant Cas9 protein and hybridizes to a target sequence of the target nucleic acid, thereby guiding the complex to the target sequence.
14. The method of claim 13 , wherein the method results in modification of the target nucleic acid.
15. The method of claim 14 , wherein said modification is cleavage.
16. The method of claim 15 , wherein the variant Cas9 protein has nickase activity that cleaves the complementary strand of a target nucleic acid, but does not cleave the non-complementary strand of a target nucleic acid.
17. The method of claim 15 , wherein the system comprises a donor polynucleotide comprising a donor sequence, and the method results in the incorporation of the donor sequence into the target nucleic acid.
18. The method of claim 13 , wherein the system comprises a PAMmer.
19. The method of claim 13 , wherein the variant Cas9 protein lacks cleavage activity.
20. The method of claim 13 , wherein the variant Cas9 protein includes a fusion partner that provides for an activity selected from: nuclease activity, methyltransferase activity, demethylase activity, DNA repair activity, DNA damage activity, deamination activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer forming activity, integrase activity, transposase activity, recombinase activity, polymerase activity, ligase activity, helicase activity, photolyase activity, glycosylase activity, methyltransferase activity, demethylase activity, acetyltransferase activity, deacetylase activity, kinase activity, phosphatase activity, ubiquitin ligase activity, deubiquitinating activity, adenylation activity, deadenylation activity, SUMOylating activity, deSUMOylating activity, ribosylation activity, deribosylation activity, myristoylation activity, and demyristoylation activity.