Compositions and methods for gene targeting using CRISPR-Cas and transposons
Provided are compositions and methods for transposon-CRISPR-based DNA editing. The compositions and methods include a modified TnsA protein that is altered from its original sequence found in Aeromonas salmonicida , and provides improved transposition frequency, and is functional in a heterologous system. The TnsA protein is used in a system with transposon proteins TnsB, TnsC, TniQ, Cas proteins Cas8f, CasSf, Cas7f, Cas6f, a transposable DNA cargo sequence that is flanked by left and right transposon sequences, and at least one guide RNA that contains at least one spacer targeted to a target DNA sequence in the chromosome or the extrachromosomal element.
1. A method for modifying a chromosome or extrachromosomal element in one or more prokaryotic cells, the method comprising introducing into the one or more prokaryotic cells a TnsA transposon protein that is at least 90% similar to SEQ ID NO:1 but contains an amino acid other than Alanine at position 125 of SEQ ID NO:1; or an expression vector comprising a tnsA gene that encodes and expresses said TnsA transposon protein when introduced into the one or more prokaryotic cells;
wherein the one or more prokaryotic cells also comprise during said modifying:
transposon proteins TnsB, TnsC, TniQ,
Cas proteins Cas8f, Cas5f, Cas7f, Cas6f,
a transposable DNA cargo sequence that is flanked by left and right transposon sequences; and
at least one guide RNA comprising a spacer targeted to a target DNA sequence in the chromosome or the extrachromosomal element, the DNA target sequence comprising a protospacer and a protospacer adjacent motif (PAM) that is 5′ to the protospacer;
wherein the TnsA, TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, Cas6f, and the at least one guide RNA, participate in transposition of the transposable DNA cargo sequence into the chromosome or extrachromosomal element in a location that is 3′ relative to the PAM and the protospacer.
2. The method of claim 1 , wherein the TnsA transposon protein is at least 90% similar to SEQ ID NO:1 and comprises a D at position 125 of SEQ ID NO:1.
3. The method of claim 2 , wherein the TnsA transposon protein comprises SEQ ID NO:2.
4. The method of claim 1 , wherein efficiency of transposition of the transposable DNA cargo in a population of prokaryotic cells is more efficient than transposition obtained from a control using a TnsA transposon protein that comprises an amino acid sequence that is at least 90% similar to SEQ ID NO:1 and contains an Alanine at position 125.
5. The method of claim 4 , wherein at least one of the TnsA, TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, and Cas6f proteins is expressed in the one or more prokaryotic cells from an expression vector.
6. The method of claim 5 , wherein the TnsA protein is expressed from an expression vector, and wherein at least one of TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, Cas6f, is also expressed from the same expression vector.
7. The method of claim 6 , wherein the TnsA, TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, Cas6f, are all expressed from the same expression vector.
8. The method of claim 5 , wherein the at least one guide RNA is introduced into the one or more prokaryotic cells as an RNA polynucleotide.
9. The method of claim 5 , wherein the at least one guide RNA is expressed from an expression vector within the one or more prokaryotic cells.
10. The method of claim 9 , wherein the expression vector that expresses the guide RNA also comprises the transposable DNA cargo.
11. The method of claim 9 , wherein the expression vector that expresses the at least one guide RNA is distinct from an expression vector that expresses at least one of the TnsA, TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, and Cas6 proteins.
12. The method of claim 10 , wherein the expression vector that expresses the at least one guide RNA is distinct from an expression vector that expresses at least one of the TnsA, TnsB, TnsC, TniQ, Cas8f, Cas5f, Cas7f, and Cas6 proteins.
13. The method of claim 1 , wherein the TnsA, TnsB, TnsC, TniQ, cas8f, cas5f, cas7f, and cas6f proteins are expressed within the one or more prokaryotic cells from the same expression vector, wherein the at least one guide RNA is expressed from an expression vector within the one or more prokaryotic cells that is distinct from the expression vector that expresses the TnsA, TnsB, TnsC, TniQ, cas8f, cas5f, cas7f and cas6f proteins, wherein the expression vector that expresses the guide RNA also comprises the transposable DNA cargo, and wherein TnsA protein comprises the sequence of SEQ ID NO:2.
14. The method of claim 13 , wherein the transposable DNA cargo sequence is transposed into the chromosome or extrachromosomal element wherein the transposable DNA cargo sequence is transposed into the chromosome or extrachromosomal element within 42-52 nucleotides 3′ relative to the 3′ end of the protospacer.