Abstract: The present application discloses a polypeptide assay system that includes a non-mammalian cell in a non-mammalian cell culture medium expressing a heterologous polypeptide that is either displayed on its cell surface such that the polypeptide is the predominant polypeptide displayed on the cell surface or the polypeptide is secreted, and a target mammalian cell that includes a reporter construct in a mammalian cell culture medium.

Abstract: A method is provided for detecting the interaction between a first test protein and a second test protein, in vivo, using reconstitution of the activity of a transcriptional activator. This reconstitution makes use of chimeric genes which express hybrid proteins. Two types of hybrid proteins are prepared. The first hybrid contains the DNA-binding domain of a transcriptional activator fused to the first test protein. The second hybrid protein contains a transcriptional activation domain fused to the second test protein. If the two test proteins are able to interact, they bring into close proximity the two domains of the transcriptional activator. This proximity is sufficient to cause transcription, which can be detected by the activity of a marker gene which contains a binding site for the DNA-binding domain.

Abstract: A method and kit are provided for detecting the interaction between a first test protein and a second test protein, in vivo, using reconstitution of the activity of a transcriptional activator. This reconstitution makes use of chimeric genes which express hybrid proteins. Two types of hybrid proteins are prepared. The first hybrid contains the DNA-binding domain of a transcriptional activator fused to the first test protein. The second hybrid protein contains a transcriptional activation domain fused to the second test protein. If the two test proteins are able to interact, they bring into close proximity the two domains of the transcriptional activator. This proximity is sufficient to cause transcription, which can be detected by the activity of a marker gene which contains a binding site for the DNA-binding domain.

Abstract: Methods are provided for detecting the interaction between a first test protein and a second test protein, in vivo, using reconstitution of the activity of a transcriptional activator. This reconstitution makes use of chimeric genes which express hybrid proteins. Two types of hybrid proteins are prepared. The first hybrid contains the DNA-binding domain of a transcriptional activator fused to the first test protein. The second hybrid protein contains a transcriptional activation domain fused to the second test protein. If the two test proteins are able to interact, they bring into close proximity the two domains of the transcriptional activator. This proximity is sufficient to cause transcription, which can be detected by the activity of a marker gene which contains a binding site for the DNA-binding domain.