Abstract: The invention relates to fusion proteins comprising at least three domains, where a first domain facilitates membrane localization of the fusion protein in a cellular context, and a second domain has or presumably has a ligand-binding function of a nuclear receptor, a third domain has an activity able to activate a signal pathway connected to a Ras protein in a cell, characterized in that when there is a lack of binding or, alternatively, when there is binding of ligand to the second domain the third domain cannot exert its activity to activate a signal pathway connected to a Ras protein in a cell, despite membrane localization. It additionally comprises inter alia cells which comprise such fusion proteins, assay methods using such cells, which are used inter alia for detecting specific interactions between ligand-binding sections of nuclear receptors and ligands, and kits for use in these assays.

Abstract: The invention concerns methods to increase the expression of genes brought into eukaryotic cells or organisms. By flanking a transcription unit EPC made up by e.g. an enhancer (E), promoter (P), and the (structural) gene of interest (C) with attachment-elements (A) the expression of said (structural) gene of interest is stimulated when integrated into the genome of eucaryotic cells and is independent of its chromosomal position. Thus a construct AEPCA is advantageous because it constitutes an independant regulatory unit.