Tn5 transposase mutants and the use thereof
Tn5 transposase (Tnp) mutants that have higher transposase activities than the wild-type Tnp are disclosed. The Tn5 Tnp mutants differ from the wild-type Tnp at amino acid positions 54, 242, and 372 and have greater avidity than the wild-type Tnp for at least one of a wild-type Tn5 outside end sequence as defined by SEQ ID NO:3 and a modified Tn5 outside end sequence as defined by SEQ ID NO:5. Also disclosed are various systems and methods of using the Tnp mutants for in vitro or in vivo transposition.
1. A polypeptide comprising a Tn5 transposase mutant modified relative to SEQ ID NO:2, the transposase mutant comprising a mutation at position 54 of SEQ ID NO:2, a mutation at position 242of SEQ ID NO:2, and a mutation at position 372of SEQ ID NO:2, wherein the transposase mutant has greater avidity than wild-type Tn5 transposase for at least one of a Tn5 outside end sequence as defined by SEQ ID NO:3 and a modified Tn5 outside end sequence as defined by SEQ ID NO:5.
2. A polypeptide as claimed in claim 1 wherein the mutation at position 54 of the Tn5 transposase mutant is a substitution mutation.
3. A polypeptide as claimed in claim 2 wherein position 54 of the Tn5 transposase mutant is a lysine.
4. A polypeptide as claimed in claim 2 wherein position 54 of the Tn5 transposase mutant is a valine.
5. A polypeptide as claimed in claim 1 wherein the mutation at position 372 of the Tn5 transposase mutant is a substitution mutation.
6. A polypeptide as claimed in claim 5 wherein position 372 of the Tn5 transposase mutant is a proline.
7. A polypeptide as claimed in claim 5 wherein position 372 of the Tn5 transposase mutant is a glutamine.
8. A polypeptide as claimed in claim 1 wherein the mutation at position 242 of the Tn5 transposase mutant is a substitution mutation.
9. A polypeptide as claimed in claim 8 wherein position 242 of the Tn5 transposase mutant is an amino acid selected from the group consisting of alanine, glycine, valine, leucine, isoleucine, tyrosine, phenylalanine, and aspartic acid.
10. A polypeptide as claimed in claim 1 wherein the Tn5 transposase mutant further comprises a substitution mutation at position 56of SEQ ID NO:2, wherein the transposase mutant lacks an inhibitor activity.
11. A polypeptide as claimed in claim 10 wherein position 56 of the Tn5 transposase mutant is an alanine.
12. A Tn5 transposase mutant modified relative to SEQ ID NO:2, the transposase mutant comprising a mutation at position 54of SEQ ID NO:2, a mutation at position 242of SEQ ID NO:2, and a mutation at position 372of SEQ ID NO:2, wherein the transposase mutant has greater avidity than wild-type Tn5 transposase for at least one of a Tn5 outside end sequence as defined by SEQ ID NO:3 and a modified Tn5 outside end sequence as defined by SEQ ID NO:5.
13. A nucleic acid comprising a polynucleotide that encodes the Tn5 transposase mutant as claimed in claim 12 .
14. A nucleic acid as claimed in claim 13 further comprising a transcriptional control sequence operably linked to the polynucleotide that encodes the Tn5 transposase mutant.
15. A host cell comprising a nucleic acid as claimed in claim 13 .
16. A system for transposing a transposable DNA sequence in vitro, the system comprising:
the polypeptide of claim 1 ;
a donor DNA molecule comprising the transposable DNA sequence, the transposable DNA sequence being flanked at its 5′- and 3′-ends by sequences selected from the group consisting of a wild-type Tn5 outside end sequence and a modified Tn5 outside end sequence that is active for in vitro transposition; and
a target DNA molecule into which the transposable DNA sequence can transpose.
17. A method for in vitro transposition, the method comprising the steps of:
combining a donor DNA molecule that comprises a transposable DNA sequence of interest with a target DNA molecule and the polypeptide of claim 1 in a suitable reaction buffer for a period of time sufficient for the enzyme to catalyze in vitro transposition,
wherein the transposable DNA sequence of interest is flanked at its 5′- and 3′-ends by a pair of sequences selected from the group consisting of a wild-type Tn5 outside end sequence and modified Tn5 outside end sequences that are active for in vitro transposition.
18. A method for in vitro transposition in a genetic construct that comprises a transposable portion and a donor backbone portion, the transposable portion comprising an origin of replication, a nucleotide sequence of interest, and a pair of sequences flanking the donor backbone portion, the pair of sequences being selected from the group consisting of a wild-type Tn5 outside end sequence and modified Tn5 outside end sequences that are active for in vitro transposition, the method comprising the steps of:
combining, in an in vitro reaction mix, the polypeptide of claim 1 and the genetic construct at a concentration suitable for generating intramolecular transposition, to generate reaction products;
transforming the reaction products into a host cell;
proliferating the host cell to generate multiple transformed cells; and
selecting from among the multiple transformed cells for cells that comprise (i) a DNA molecule that has lost the donor backbone portion and (ii) a transposition of the nucleotide sequence of interest.
19. A method for forming a synaptic complex between (a) the polypeptide of claim 1 and (b) a polynucleotide that comprises a pair of sequences and a transposable nucleotide sequence therebetween, wherein the pair of sequences are selected from the group consisting of a wild-type Tn 5 outside end sequence and modified Tn5 outside end sequences that are active for in vitro transposition, the method comprising the step of:
combining (a) and (b) in vitro under conditions that disfavor polynucleotide strand transfer to form the synaptic complex.
20. A method for making an insertional mutation in cellular nucleic acid in a target cell, the method comprising the step of:
introducing into the target cell a synaptic complex according to claim 19 under conditions that mediate transpositions into the cellular nucleic acid.