Methods and compositions for prime editing nucleotide sequences
Compositions and methods are provided herein for conducting prime editing of a target DNA molecule (e.g., a genome) that enables the incorporation of a nucleotide change and/or targeted mutagenesis. The compositions include fusion proteins comprising nucleic acid programmable DNA binding proteins (napDNAbp) and a polymerase (e.g., reverse transcriptase), which is guided to a specific DNA sequence by a modified guide RNA, named an PEgRNA. The PEgRNA has been altered (relative to a standard guide RNA) to comprise an extended portion that provides a DNA synthesis template sequence which encodes a single strand DNA flap which is synthesized by the polymerase of the fusion protein and which becomes incoporated into the target DNA molecule.
1 . A multiplex prime editing system comprising:
a) a prime editor, or one or more polynucleotides encoding the prime editor, the prime editor comprising:
i) a nucleic acid programmable DNA binding protein (napDNAbp) that is a nickase configured to cut a non-target strand of a double-stranded DNA sequence or a nuclease configured to cut both strands of the double-stranded DNA sequence; and
ii) a reverse transcriptase domain;
b) a first prime editing guide RNA (first PEgRNA), or one or more polynucleotides encoding the first PEgRNA, wherein the first PEgRNA comprises:
i) a first spacer sequence complementary to a first target sequence in a first target strand at a first genomic site;
ii) a first gRNA core capable of complexing with the napDNAbp;
iii) a first RNA extension arm comprising: (A) a first DNA synthesis template comprising a first edit template that encodes one or more edits compared to a region downstream of a first cut site in a first non-target strand at the first genomic site, and (B) a first primer binding site that is complementary to a region upstream of the first cut site in the first non-target strand at the first genomic site; and
c) a second prime editing guide RNA (second PEgRNA), or one or more polynucleotides encoding the second PEgRNA, wherein the second PEgRNA comprises:
i) a second spacer sequence complementary to a second target sequence in a second target strand at a second genomic site;
ii) a second gRNA core capable of complexing with the napDNAbp;
iii) a second RNA extension arm comprising: (A) a second DNA synthesis template comprising a second edit template that encodes one or more edits compared to a region downstream of a second cut site in a second non-target strand at the second genomic site, and (B) a second primer binding site that is complementary to a region upstream of the second cut site in the second non-target strand at the second genomic site.
2 . The multiplex prime editing system of claim 1 , wherein the region upstream of the first cut site to which the first primer binding site is complementary is immediately 5′ of the first cut site; and wherein the region upstream of the second cut site to which the second primer binding site is complementary is immediately 5′ of the second cut site.
3 . The multiplex prime editing system of claim 1 , wherein the first cut site is three nucleotides upstream of a protospacer adjacent motif (PAM) in the first non-target strand at the first genomic site; and wherein the second cut site is three nucleotides upstream of a protospacer adjacent motif (PAM) in the second non-target strand at the second genomic site.
4 . The multiplex prime editing system of claim 1 , wherein the first primer binding site and the second primer binding site are each from 7 to 17 nucleotides in length.
5 . The multiplex prime editing system of claim 4 , wherein the first primer binding site and/or the second primer binding site is from 8 to 15 nucleotides in length.
6 . The multiplex prime editing system of claim 1 , wherein the first spacer sequence and the second spacer sequence are each 20 nucleotides in length.
7 . The multiplex prime editing system of claim 6 , wherein the first primer binding site comprises the reverse complement of nucleotides p to 17 of the first spacer sequence, wherein p is an integer no greater than 13; and wherein the second primer binding site comprises the reverse complement of nucleotides q to 17 of the second spacer sequence, wherein q is an integer no greater than 13.
8 . The multiplex prime editing system of claim 1 , wherein the first DNA synthesis template further comprises a first homology arm that is complementary to a region downstream of the first cut site in the first non-target strand at the first genomic site; and wherein the second DNA synthesis template further comprises a second homology arm that is complementary to a region downstream of the second cut site in the second non-target strand at the second genomic site.
9 . The multiplex prime editing system of claim 8 , wherein the first homology arm is located 5′ of the first edit template; and wherein the second homology arm is located 5′ of the second edit template.
10 . The multiplex prime editing system of claim 9 , wherein the first RNA extension arm comprises, from 5′ to 3′, the first homology arm, the first edit template, and the first primer binding site; and wherein the second RNA extension arm comprises, from 5′ to 3′, the second homology arm, the second edit template, and the second primer binding site.
11 . The multiplex prime editing system of claim 10 , wherein the first edit template is directly adjacent to the first primer binding site; and wherein the second edit template is directly adjacent to the second primer binding site.
12 . The multiplex prime editing system of claim 1 , wherein the first DNA synthesis template is from 10 to 16 nucleotides in length; and/or wherein the second DNA synthesis template is from 10 to 16 nucleotides in length.
13 . The multiplex prime editing system of claim 1 , wherein the first DNA synthesis template is from 12 to 17 nucleotides in length; and/or wherein the second DNA synthesis template is from 12 to 17 nucleotides in length.
14 . The multiplex prime editing system of claim 1 , wherein the first DNA synthesis template is less than 15 nucleotides in length; and/or wherein the second DNA synthesis template is less than 15 nucleotides in length.
15 . The multiplex prime editing system of claim 1 , wherein at least one of the edits encoded by the first DNA synthesis template disrupts an endogenous PAM site associated with the first spacer sequence; and/or wherein at least one of the edits encoded by the second DNA synthesis template disrupts an endogenous PAM site associated with the second spacer sequence.
16 . The multiplex prime editing system of claim 1 , wherein the first PEgRNA is a single molecule comprising the first spacer sequence, the first gRNA core, and the first RNA extension arm; and wherein the second PEgRNA is a single molecule comprising the second spacer sequence, the second gRNA core, and the second RNA extension arm.
17 . The multiplex prime editing system of claim 16 , wherein the first PEgRNA comprises, from 5′ to 3′, the first spacer sequence, the first gRNA core, and the first RNA extension arm; and wherein the second PEgRNA comprises, from 5′ to 3′, the second spacer sequence, the second gRNA core, and the second RNA extension arm.
18 . The multiplex prime editing system of claim 1 , wherein the first PEgRNA and/or the second PEgRNA comprises at least one of a modified nucleobase, a modified sugar, a modified phosphate group, or a nucleoside analog.
19 . The multiplex prime editing system of claim 1 , wherein the first PEgRNA and/or the second PEgRNA comprises one or more 3′ structures selected from the group consisting of linkers, stem loops, hairpins, toeloops, tetraloops, aptamers, and RNA-protein recruitment domains.
20 . The multiplex prime editing system of claim 1 , wherein the first PEgRNA and/or the second PEgRNA comprises an aptamer capable of recruiting an effector domain.
21 . The multiplex prime editing system of claim 1 , wherein the napDNAbp is a Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-Cas effector protein.
22 . The multiplex prime editing system of claim 21 , wherein the napDNAbp comprises a RuvC nuclease domain, a HNH nuclease domain, or both.
23 . The multiplex prime editing system of claim 22 , wherein the napDNAbp comprises the RuvC nuclease domain and the HNH nuclease domain.
24 . The multiplex prime editing system of claim 22 , wherein the napDNAbp is a Cas9 nickase or a Cas9 nuclease.
25 . The multiplex prime editing system of claim 1 , wherein the reverse transcriptase domain is from a retrovirus or a retrotransposon.
26 . The multiplex prime editing system of claim 1 , wherein the reverse transcriptase domain is a Moloney-Murine Leukemia Virus reverse transcriptase (M-MLV RT).
27 . The multiplex prime editing system of claim 1 , wherein the nucleic acid programmable DNA binding protein and the reverse transcriptase domain are connected to form a fusion protein.
28 . The multiplex prime editing system of claim 1 , further comprising a first single guide RNA capable of directing the napDNAbp to the first non-target strand downstream of the first cut site at the first genomic site.
29 . The multiplex prime editing system of claim 1 , wherein the first genomic site and the second genomic site are on separate chromosomes.
30 . The multiplex prime editing system of claim 20 , wherein the aptamer is a MS2 aptamer.
31 . The multiplex prime editing system of claim 23 , wherein the HNH nuclease domain comprises one or more mutations that decrease or eliminate nuclease activity.
32 . The multiplex prime editing system of claim 28 , further comprising a second single guide RNA capable of directing the napDNAbp to the second non-target strand downstream of the second cut site at the second genomic site.