Expression cassette

1. A nucleic acid construct comprising the following (i) to (iv):

(i) an expression regulatory region having a promoter and a transcriptional activator-binding region sequence;

(ii) a nucleic acid encoding a transcriptional activator which is capable of binding to the expression regulatory region, wherein the nucleic acid is operably linked to the first expression regulatory region,

(iii) a) a nucleic acid for expressing a target product that is operably linked to the second expression regulatory region or b) a site into which a nucleic acid for expressing a target product is insertable so that the nucleic acid is operably linked to the second expression regulatory region; and

(iv) an internal ribosome entry site (IRES) sequence or a sequence encoding 2A peptide that is inserted between (ii) and (iii);

wherein the promoter is selected from CMV promoter, SV40 promoter, EF-1α promoter, CAG promoter, and PGK promoter,

wherein the transcriptional activator is Tat of immunodeficiency virus or a functionally homologous variant thereof, wherein the functionally homologous variant consists of an amino acid sequence having 95% or more identity to the amino acid sequence encoded by the base sequence of SEQ ID NO: 1, and

wherein the transcriptional activator-binding region is a trans-activation-responsive region of immunodeficiency virus or a functionally homologous sequence thereof, wherein the functionally homologous sequence has 95% or more homology to the base sequence of SEQ ID NO: 2.

2. A method for producing a target product in a mammalian cell comprising the following steps (a) to (d):

(a) introducing into a cell the nucleic acid construct of claim 1 ;

(b) culturing the cell obtained in the step (a);

(c) expressing the target product by the step (b); and

(d) obtaining the expressed target product.

3. A method for producing a cell expressing a target product in vitro, comprising a step of introducing into a mammalian cell the nucleic acid construct of claim 1 .

4. A kit comprising the nucleic acid construct of claim 1 .

5. A set of nucleic acid constructs, comprising the following (1) and (2):

(1) a first nucleic acid construct comprising a first expression cassette comprising:

(i) a first expression regulatory region having a first promoter and a first transcriptional activator-binding region sequence; and

(ii) a nucleic acid encoding a transcriptional activator which is capable of binding to the first expression regulatory region, wherein the nucleic acid is operably linked to the first expression regulatory region, and

(2) a second nucleic acid construct comprising a second expression cassette comprising:

(i) a second expression regulatory region having a second promoter and a second transcriptional activator-binding region sequence; and

(ii) a) a nucleic acid for expressing a target product that is operably linked to the second expression regulatory region or b) a site into which a nucleic acid for expressing a target product is insertable so that the nucleic acid is operably linked to the second expression regulatory region,

wherein the first and second promoters are each independently selected from the group consisting of CMV promoter, SV40 promoter, EF-1α promoter, CAG promoter, and PGK promoter,

wherein the first and second promoters are the same or different,

wherein the first and second expression regulatory region are the same or different, wherein the transcriptional activator is Tat of immunodeficiency virus or a functionally homologous variant thereof, wherein the functionally homologous variant consists of an amino acid sequence having 95% or more identity to the amino acid sequence encoded by the base sequence of SEQ ID NO: 1, and

wherein the first and second transcriptional activator-binding regions are each independently a trans-activation-responsive region of immunodeficiency virus or a functionally homologous sequence thereof, wherein the functionally homologous sequence has 95% or more homology to the base sequence of SEQ ID NO: 2,

wherein the first and second transcriptional activator-binding regions are the same or different, and

wherein the first nucleic acid construct and the second nucleic acid construct do not comprise an origin of replication wherein the origin of replication allows for replication in an animal cell.

6. A method for producing a target product in a mammalian cell comprising the following steps (a) to (d):

(a) introducing into a cell the set of nucleic acid constructs of claim 5 ;

(b) culturing the cell obtained in the step (a);

(c) expressing the target product by the step (b); and

(d) obtaining the expressed target product.

7. A method for producing a cell expressing a target product in vitro, comprising a step of introducing into a mammalian cell the set of nucleic acid constructs of claim 5 .

8. A kit comprising the set of nucleic acid constructs of claim 5 .