Highly inducible dual-promoter lentiviral TET-ON system
The invention relates to expression systems useful for regulated expression of a gene of interest based on the constitutive expression of the original TetR repressor and the expression of the polynucleotide driven by a constitutive promoter operably linked to an operator sequence for a tetracycline operator sequence. The system can be provided as two different polynucleotides or as an all-in-one vector. The invention also relates to vectors, host cells and viral particles according to the invention as well as to the uses thereof for in vitro and in vivo production of products of interest or for therapy.
1. A polynucleotide comprising
(i) a transcriptional regulatory sequence comprising a first promoter and at least one binding site for a transcriptional repressor wherein said first promoter and said binding site for a transcriptional repressor are arranged so that the binding of the transcriptional repressor to said binding site inhibits the transcriptional activity of the promoter and
(ii) an expression cassette comprising a polynucleotide encoding a regulatable transcriptional repressor under the operative control of a second promoter wherein said regulatable transcriptional repressor is capable of specifically binding to the binding site in the transcriptional regulatory sequence in the absence but not in the presence of a ligand thereof,
wherein the first promoter is the cytomegalovirus (CMV) immediate early promoter, wherein the second promoter is the spleen focus forming virus long terminal repeat (SFFV LTR) promoter; and
wherein the transcriptional activity of the first promoter differs by less than 10% from the transcriptional activity of said first promoter when the transcriptional regulatory sequence (i) and the expression cassette (ii) are found in separate vectors.
2. The polynucleotide according to claim 1 wherein the binding site for a transcriptional repressor comprises at least a TetO operator sequence and wherein the regulatable transcriptional repressor is the tetracycline repressor.
3. The polynucleotide according to claim 1 wherein the binding site for the transcriptional repressor is downstream of the first promoter.
4. The polynucleotide according to claim 1 , wherein the regulatable transcriptional repressor further comprises a nuclear localization signal.
5. The polynucleotide according to claim 1 further comprising a polynucleotide of interest under operative control of the transcriptional regulatory sequence.
6. An expression vector comprising the polynucleotide according to claim 1 .
7. A lentiviral particle comprising the vector according to claim 6 .
8. A host cell comprising the vector according to claim 6 .
9. A composition or kit-of-parts comprising
(i) a first polynucleotide comprising transcriptional regulatory sequence comprising a first promoter and at least one binding site for a transcriptional repressor wherein said first promoter and said binding site are arranged so that the binding of the transcriptional repressor to said binding site inhibits the transcriptional activity of the promoter, and
(ii) a second polynucleotide comprising an expression cassette comprising a polynucleotide encoding a regulatable transcriptional repressor under the operative control of a second promoter wherein said regulatable transcriptional repressor is capable of specifically binding to the binding site in the transcriptional regulatory sequence in the absence but not in the presence of a ligand thereof, wherein the first promoter is the cytomegalovirus (CMV) immediate early promoter,
wherein the second promoter is the spleen focus forming virus long terminal repeat (SFFV LTR) promoter; and
wherein the first promoter differs by less than 10% from the transcriptional activity of said first promoter when the transcriptional regulatory sequence (i) and the expression cassette (ii) are found in separate vectors.
10. A composition or kit-of-parts according to claim 9 wherein the binding site for a transcriptional repressor is a binding site for the tetracycline repressor and wherein the regulatable transcriptional repressor is the tetracycline repressor.
11. A composition or kit-of-parts according to claim 10 wherein the binding site for the tetracycline repressor is a TetO operator sequence.
12. A composition or kit-of-parts according to claim 9 further comprising a ligand of the transcriptional repressor which, when bound to the repressor, results in the inactive repressor which is no longer capable of binding to its binding site in the transcriptional regulatory sequence.
13. A method for regulating the expression of a nucleic acid sequence of interest comprising the steps of
(i) providing a host cell comprising the polynucleotide according to claim 1 wherein the nucleic acid of interest is operatively linked to the first promoter in said polynucleotide, and
(ii) contacting said host cell which with a ligand for the transcriptional repressor wherein said ligand is capable of binding to the transcriptional repressor producing an inactive repressor which is released from its binding site in the transcriptional regulatory sequence thereby allowing the transcription of the nucleic acid driven by the first promoter.
14. A method for regulating the expression of a nucleic acid sequence of interest comprising the steps of
(i) providing a host cell comprising the first and second polynucleotides of the composition or kit-of-parts according to claim 9 wherein the nucleic acid is operatively linked to the first promoter of the first polynucleotide, and
(ii) contacting said host cell which with a ligand for the transcriptional repressor wherein said ligand is capable of binding to the transcriptional repressor producing an inactive repressor which is released from its binding site in the transcriptional regulatory sequence thereby allowing the transcription of the nucleic acid driven by the first promoter.