The present disclosure relates to nucleobase editors and methods of use thereof. Disclosed herein are fusion proteins, systems, and compositions for editing disease-associated mutations and methods of use thereof. In some aspects, disclosed herein is a fusion protein comprising a Cas9 nickase and a nucleotide deaminase, wherein the Cas9 nickase comprises a first amino acid substitution at a position selected from the group consisting of 262, 324, 409, 480, 543, 694, and 1219 when compared to SEQ ID NO: 11, and wherein the Cas9 nickase comprises a second amino acid substitution at a position selected from the group consisting of 1111, 1135, 1218, 1219, 1322, 1335, and 1337 when compared to SEQ ID NO: 11.

Aspects of the disclosure relate to methods, compositions, and systems for editing a DNA sequence encoding an endogenous tRNA into a suppressor tRNA using base editing (e.g., to treat a disease caused by a premature termination codon or PTC). Additional aspects relate to compositions comprising a gRNA configured to bind to a DNA sequence encoding an endogenous tRNA. Other aspects relate to complexes comprising a base editor and a gRNA that are capable of editing an endogenous tRNA into a suppressor tRNA. In some aspects, the disclosure further relates to polynucleotides encoding one or more nucleic acid sequences encoding the gRNAs, vectors comprising the polynucleotides, and/or cells comprising the polynucleotides, complexes, gRNAs, and/or vectors disclosed herein. Additional aspects further relate to kits comprising any one of the compositions, complexes, gRNAs, polynucleotides, vectors, and/or cells disclosed herein.