Abstract: A method for detecting an inhibitory effect of a test gene on intracellular signal transduction is provided, which comprises transforming host cells by a vector carrying a gene capable of inducing cell death under specific conditions and having been ligated downstream to a promoter functioning in response to specific extracellular stimulation, introducing a test substance into the host cells or treating the host cells with the test substance so as to exracellularly stimulate the same, and then examining whether the cells survive or not to thereby detect whether the test substance has an inhibitory effect on intracellular signal transduction or not. Another detection method uses a reporter gene in place of the gene capable of inducing cell death. Furthermore, a method for isolating a gene having an inhibitory effect on intracellular signal transduction is provided, which comprises introducing a gene library into the host cells, screening surviving cells, and then isolating the introduced gene from the cells.

Abstract: A protein having transcription inhibitory activity and lacking at least a part of regions other than a region having DNA binding activity in a transcriptional regulatory factor is provided. This protein can be obtained by isolating cDNA encoding a protein capable of binding to the transcriptional regulatory region of the gene transcription of which is to be inhibited, deleting from the cDNA at least a part of the regions other than the region having DNA-binding activity, inserting the resulting DNA into an appropriate vector, introducing said vector into cells to allow them to express the deleted gene, and isolating and purifying a protein showing the transcription inhibitory activity. For example, the protein can be used in the field of pharmaceuticals as a therapeutic agent. Its use in the field of gene therapy is also expected.

Abstract: A protein having transcription inhibitory activity and lacking at least a part of regions other than a region having DNA binding activity in a transcriptional regulatory factor is provided. This protein can be obtained by isolating cDNA encoding a protein capable of binding to the transcriptional regulatory region of the gene transcription of which is to be inhibited, deleting from the cDNA at least a part of the regions other than the region having DNA-binding activity, inserting the resulting DNA into an appropriate vector, introducing said vector into cells to allow them to express the deleted gene, and isolating and purifying a protein showing the transcription inhibitory activity. For example, the protein can be used in the field of pharmaceuticals as a therapeutic agent. Its use in the field of gene therapy is also expected.

Abstract: This invention relates to a spin filter assembly and its usage to facilitate the isolation and analyses of molecules and compounds such as proteins present in various biological and non-biological solutions. The spin filter assembly of this invention comprise of a tube having an open top end, a bottom end opposite the open top end, a body of a first length, an inner diameter and a first outer diameter, a filter means at the bottom end, the tube insertable to an upper portion of a centrifuge holder having a closed lower end, an open upper end, a length longer than the first length of the tube, and a second inner diameter greater than the first outer diameter of the tube; and, a container closure means that fits on top of the open end of the tube. The spin filter assembly can be a component of a sample preparation or assay kit, for example, a kit for analyzing proteins by immunoprecipitation. A process for analyzing proteins by immunoprecipitation using the spin filter assembly is described.