Abstract: Transgenic mice carrying a transgene comprising a nucleic acid molecule encoding protein useful for regulating the expression of genes in eukaryotic cells in a highly controlled manner are disclosed. In the regulatory system of the invention, transcription of a tet operator-linked nucleotide sequence is stimulated by a transcriptional activator fusion protein composed of two polypeptides, a first polypeptide which binds to tet operator sequences in the presence of tetracycline operatively linked to a second polypeptide activates transcription in eukaryotic cells. In a preferred embodiment, the transgene encoding the transcriptional activator fusion protein is integrated at a predetermined location within the chromosome of the transgenic mouse.

Abstract: A method for regulating expression of a tet operator-linked gene in a cell of a subject is disclosed. In one embodiment, the method involves introducing into the cell a nucleic acid molecule encoding a tetracycline-controllable transactivator (tTA), the tTA comprising a Tet repressor operably linked to a polypeptide which directly or indirectly activates transcription in eucaryotic cells; and modulating the concentration of a tetracycline, or analogue thereof, in the subject. Alternatively, in another embodiment, the method involves obtaining the cell from the subject, introducing into the cell a first nucleic acid molecule which operatively links a gene to at least one tet operator sequence, introducing into the cell a second nucleic acid molecule encoding a tTA, to form a modified cell, administering the modified cell to the is subject, and modulating the concentration of a tetracycline, or analogue thereof, in the subject. The first and second nucleic acid molecule can be within a single molecule (e.g.

Abstract: Transgenic animals carrying a transgene comprising a nucleic acid molecule encoding protein useful for regulating the expression of genes in eukaryotic cells and organisms in a highly controlled manner are disclosed. In the regulatory system of the invention, transcription of a tet operator-linked nucleotide sequence is inhibited by a transcriptional inhibitor fusion protein composed of two polypeptides, a first polypeptide which binds to tet operator sequences and a second polypeptide which directly or indirectly inhibits transcription in eukaryotic cells. In various embodiment, the first polypeptide binds to tet operator sequences either: (i) in the absence but not the presence of tetracycline (or an analogue thereof) or (ii) in the presence but not the absence of tetracycline (or an analogue thereof). In a preferred embodiment, the transgene encoding the transcriptional inhibitor fusion protein is integrated at a predetermined location within the chromosome of the transgenic animal.

Abstract: Transgenic mice carrying two transgenes, the first coding for a transactivator fusion protein comprising a tet repressor and a polypeptide which directly or indirectly activates transcription of a tet operator-linked gene in eucaryotic cells, and the second comprising a gene operably linked to a minimal promotor operably linked to at least one tet operator sequence, are disclosed. Isolated DNA molecules (e.g., targeting vectors) for integrating a polynucleotide sequence encoding a transactivator of the invention at a predetermined location within a second target DNA molecule by homologous recombination are also disclosed. Transgenic mice having the DNA molecules of the invention integrated at a predetermined location in a chromosome by homologous recombination are also encompassed by the invention. Methods to regulate the expression of a tet operator linked-gene of interest by administering tetracycline or a tetracycline analogue to a mouse of the invention are also disclosed.

Abstract: Methods of regulating gene expression in subjects using tetracycline-responsive fusion proteins are disclosed. In one embodiment, the method involves introducing into a cell the subject a nucleic acid molecule encoding a fusion protein which inhibits transcription, the fusion protein comprising a first polypeptide which binds to a tet operator sequence, operatively linked to a heterologous second polypeptide which inhibits transcription in eukaryotic cells; and modulating the concentration of a tetracycline, or analogue thereof, in the subject. The first polypeptide can binds to a tet operator sequence in the absence, but not the presence, of tetracycline. Alternatively, the first polypeptide can binds to a tet operator sequence in the presence, but not the absence, of tetracycline.

Abstract: Nucleic acid molecules and proteins useful for regulating the expression of genes in eukaryotic cells and organisms in a highly controlled manner are disclosed. In the regulatory system of the invention, transcription of a tet operator-linked nucleotide sequence is inhibited by a transcriptional inhibitor fusion protein composed of two polypeptides, a first polypeptide which binds to tet operator sequences either (i) in the absence but not the presence of tetracycline (or an analogue thereof) or (ii) in the presence but not the absence of tetracycline (or an analogue thereof), and a second polypeptide which directly or indirectly inhibits transcription in eukaryotic cells. In one embodiment, the fusion protein comprises a Tet repressor operatively linked to a transcriptional silencer polypeptide. In another embodiment, the fusion protein comprises a mutated Tet repressor operatively linked to a transcriptional silencer polypeptide.

Abstract: Nucleic acid molecules and proteins useful for regulating the expression of genes in eukaryotic cells and organisms in an inducible manner are disclosed. In the regulatory system of the invention, transcription of a tet operator-linked nucleotide sequence is stimulated by a transcriptional activator fusion protein composed of two polypeptides, a first polypeptide which binds to tet operator sequences in the presence of tetracycline or a tetracycline analogue and a second polypeptide which directly or indirectly activates transcription in eukaryotic cells. In one embodiment, the fusion protein comprises a mutated Tet repressor operatively linked to a transcriptional activation polypeptide, such as a portion of herpes simplex virus virion protein 16. In the absence of an inducing agent (tetracycline or a tetracycline analogue), transcription of the tet operator-linked nucleotide sequence remains uninduced.

Abstract: Transgenic animals carrying two transgenes, the first coding for a transactivator fusion protein comprising a tet repressor and a polypeptide which directly or indirectly activates in eucaryotic cells, and the second comprising a gene operably linked to a minimal promoter operably linked to at least one tet operator sequence, are disclosed. Isolated DNA molecules (e.g., targeting vectors) for integrating a polynucleotide sequence encoding a transactivator of the invention at a predetermined location within a second target DNA molecule by homologous recombination are also disclosed. Transgenic animals having the DNA molecules of the invention integrated at a predetermined location in a chromosome by homologous recombination are also encompassed by the invention. Methods to regulate the expression of a tet operator linked-gene of interest by administering tetracycline or a tetracycline analogue to an animal of the invention are also disclosed.

Abstract: Isolated nucleic acid molecules encoding fusion proteins which regulate transcription in eukaryotic cells are disclosed. The fusion proteins of the invention comprise a Tet repressor having at least one amino acid mutation that confers on the fusion protein an ability to bind a class B tet operator sequence having a nucleotide substitution at position +4 or +6, operatively linked to a polypeptide which regulates transcription in eukaryotic cells. Methods for regulating transcription of a tet operator-linked gene in a cell are also provided.

Abstract: A first polynucleotide molecule coding for a transactivator fusion protein comprising the tet repressor and a protein capable of activating transcription in eucaryotes. A second polynucleotide molecule coding for a protein, wherein said polynucleotide is operably linked to a minimal promoter operably linked to at least one tet operator sequence is also disclosed. A method to regulate the expression of a protein coded for by a polynucleotide, by cultivating the eucaryotic cell of the invention in a medium comprising tetracycline or a tetracycline analogue is also disclosed. Kits containing the polynucleotide molecules are also disclosed.