Incorporation of unnatural amino acids into proteins using base editing
Provided herein are systems, compositions, and methods for the incorporation of unnatural amino acids into proteins via nonsense suppression or rare codon suppression. Nonsense codons and rare codons may be introduced into the coding sequence of a protein of interest using a CRISPR/Cas9-based nucleobase editor described herein. The nucleobase editors are able to be programmed by guide nucleotide sequences to edit the target codons in the coding sequence of the protein of interest. Also provided are application enabled by the technology described herein.
1. A method of incorporating an unnatural amino acid into a protein of interest at one or more specific position(s), the method comprising:
(i) contacting a polynucleotide encoding the protein of interest with a fusion protein comprising (a) a guide nucleotide sequence-programmable DNA-binding protein domain; (b) a cytosine deaminase domain; and (c) a uracil glycosylase inhibitor (UGI) domain, wherein the fusion protein is associated with a guide nucleotide sequence, and whereby the contacting results in changing a target codon to a suppressible stop codon or a rare codon via deamination of a cytosine (C) base; and
(ii) using the polynucleotide containing the suppressible stop codon or rare codon in a translation system, whereby the unnatural amino acid is incorporated into the protein of interest at the suppressible stop codon or rare codon during translation of the protein,
wherein the polynucleotide comprises a coding strand and a complementary strand.
2. The method of claim 1 , wherein the guide nucleotide sequence-programmable DNA binding protein domain is selected from the group consisting of: nuclease inactive Cas9 (dCas9) domains, nuclease inactive Cpf1 domains, nuclease inactive Argonaute domains, Cas9 nickase, and variants thereof.
3. The method of claim 1 , wherein the cytosine deaminase domain comprises an apolipoprotein B mRNA-editing complex (APOBEC) family deaminase.
4. The method of claim 1 , wherein the cytosine deaminase domain comprises the amino acid sequence of any one of SEQ ID NOs: 270-288 and 378-381, or an amino acid sequence having at least 80% sequence identity with any one of SEQ ID NOs: 270-288 or 378-381.
5. The method of claim 1 , wherein the cytosine deaminase domain and the guide nucleotide sequence-programmable DNA-binding protein domain are fused via an linker.
6. The method of claim 1 , wherein the fusion protein comprises the amino acid sequence of any one of SEQ ID NO: 291-295 and 382-386, or an amino acid sequence having at least 80% sequence identity with any one of SEQ ID NOs: 291-295 or 382-386.
7. The method of claim 1 , wherein the guide nucleotide sequence is an RNA.
8. The method of claim 1 , wherein the target codon is changed to a suppressible stop codon selected from the group consisting of TAG (Amber), TGA (Opal), and TAA (Ochre).
9. The method of claim 1 , wherein the target codon is changed to a rare codon selected from the group consisting of AGG, ATA, AGT, TTT, and TTC.
10. The method of claim 1 , wherein the translation system comprises:
(a) an orthogonal tRNA (OtRNA);
(b) an orthogonal aminoacyl tRNA synthetase (ORS); and
(c) an unnatural amino acid,
wherein the ORS preferentially aminoacylates the OtRNA with the unnatural amino acid, and the OtRNA recognizes at least one suppressible stop codon.
11. The method of claim 1 , wherein two or more types of unnatural amino acids are incorporated into the protein of interest.
12. The method of claim 1 , wherein the unnatural amino acid is incorporated into two or more proteins of interest.
13. The method of claim 1 , wherein the unnatural amino acid is incorporated proteome-wide.
14. A method of incorporating an unnatural amino acid into a protein of interest at one or more specific position(s), the method comprising:
(i) contacting a polynucleotide encoding the protein of interest with a fusion protein comprising (a) a programmable DNA-binding protein domain; (b) a cytosine deaminase domain; and (c) a uracil glycosylase inhibitor (UGI) domain, whereby the contacting results in changing a target codon to a suppressible stop codon or a rare codon via deamination of a target base; and
(ii) using the polynucleotide containing the suppressible stop codon or rare codon in a translation system, whereby the unnatural amino acids are incorporated into the protein of interest at the suppressible stop codon or rare codon during translation of the protein,
wherein the polynucleotide comprises a coding strand and a complementary strand.
15. The method of claim 1 , wherein the unnatural amino acid comprises a click chemistry handle.
16. The method of claim 14 , wherein the guide nucleotide sequence-programmable DNA binding protein domain is selected from the group consisting of: nuclease inactive Cas9 (dCas9) domains, nuclease inactive Cpf1 domains, nuclease inactive Argonaute domains, Cas9 nickase, and variants thereof.
17. The method of claim 14 , wherein the cytosine deaminase domain comprises an apolipoprotein B mRNA-editing complex (APOBEC) family deaminase.
18. The method of claim 14 , wherein the cytosine deaminase domain comprises the amino acid sequence of any one of SEQ ID NOs: 270-288 and 378-381, or an amino acid sequence having at least 80% sequence identity with any one of SEQ ID NOs: 270-288 or 378-381.
19. The method of claim 14 , wherein the fusion protein comprises the amino acid sequence of any one of SEQ ID NO: 291-295 and 382-386, or an amino acid sequence having at least 80% sequence identity with any one of SEQ ID NOs: 291-295 or 382-386.