Replicative transposon system
The invention relates to a system and method for introducing DNA into cells. In particular, the invention relates to a method for introducing single or multiple copies of a DNA sequence or gene of interest into a cell comprising providing: a) a “copy and paste” transposase; and b) a construct comprising a DNA sequence or gene of interest flanked by a “copy and paste” transposon terminal sequence, such as an LTS or RTS. A novel “copy and paste” transposon of the Helitron family is described along with systems for using the corresponding transposase in methods for introducing DNA into cells, for example, to generate cell lines for use in protein production, cell and gene therapy or as reference standards.
1. An in vitro or ex vivo method for introducing a single copy or multiple copies of a gene of interest into a mammalian cell, comprising:
a) providing a Helitron transposase, wherein the Helitron transposase is a Helraiser transposase comprising an amino acid sequence set forth in SEQ ID NO:1, or a sequence having at least 95% identity thereto;
b) providing a construct comprising a gene of interest flanked by Helitron transposase LTS sequences, wherein the LTS sequences comprise a nucleic acid sequence set forth in SEQ ID NO:3, or a sequence having at least 95% identity thereto; and
c) introducing the Helitron transposase and the construct into a mammalian cell in vitro or ex vivo, wherein the Helitron transposase and the construct are provided as two separate entities, and wherein introducing the Helitron transposase and the construct into the mammalian cell results in the introduction of a single copy or multiple copies of the gene of interest into the genome of the mammalian cell.
2. The method as claimed in claim 1 , wherein the cell is a human cell, a rat cell, a hamster cell, or a mouse cell.
3. The method as claimed in claim 1 , wherein the gene of interest is also flanked by a RTS sequence.
4. The method as claimed in claim 3 wherein the RTS sequence comprises a nucleic acid sequence as set out in SEQ ID NO: 4 or a sequence having at least 95% identity thereto.
5. The method as claimed in claim 1 , where the gene of interest is an endogenous gene or a cDNA thereof and multiple copies of the endogenous gene or the cDNA thereof are introduced into the genome of the mammalian cell.
6. The method as claimed in claim 1 , wherein the gene of interest is a non-endogenous gene or a cDNA thereof.
7. The method as claimed in claim 1 , further comprising detecting and selecting clones of the mammalian cell comprising multiple copies of said gene of interest, thereby generating a cell line, wherein said providing a Helitron transposase in step a) comprises introducing a construct comprising a nucleic acid encoding the Helitron transposase into the mammalian cell.
8. The method as claimed in claim 7 , wherein the gene of interest is also flanked by RTS sequences.
9. The method as claimed in claim 7 , wherein said selecting clones comprises selecting clones with known copy numbers of the gene of interest.
10. The method as claimed in claim 1 , wherein the gene of interest encodes a therapeutic protein.
11. A cell line produced by a method as claimed in claim 1 .
12. The method as claimed in claim 1 , wherein the cell is a Chinese hamster ovary (CHO) cell, a 293T cell, a HEK293 cell, a human induced pluripotent stem cell, a human stem cell, a murine embryonic stem cell, a hematopoietic stem cell, a T cell, or a B cell.