Abstract: The invention concerns methods for cell screening of agents capable of modulating the activity of SCF.sup.Met30 complexes comprising the following steps: (i) contacting the product to be tested with a modified yeast strain, including (a) a hybrid sequence comprising a sequence coding for a Met4 protein, in its wild or mutated form, fused in phase with at least a sequence coding for an appropriate marker, said hybrid sequence being expressed under the control of a promoter, active in the yeast and optionally (b) a reporter transcriptional system, consisting of a reporter gene placed under the control of an appropriate operating sequence or an appropriate yeast promoter, (ii) adding methionine and (iii) determining the level of expression and stability of the expressed protein from the hybrid sequence, and their uses. The invention also concerns plasmids and yeast strains capable of being used in said methods.

Abstract: The invention concerns methods for cell screening of agents capable of modulating the activity of SCFMet30 complexes comprising the following steps: (i) contacting the product to be tested with a modified yeast strain, including (a) a hybrid sequence comprising a sequence coding for a Met4 protein, in its wild or mutated form, fused in phase with at least a sequence coding for an appropriate marker, said hybrid sequence being expressed under the control of a promoter, active in the yeast and optionally (b) a reporter transcriptional system, consisting of a reporter gene placed under the control of an appropriate operating sequence or an appropriate yeast promoter, (ii) adding methionine and (iii)determining the level of expression and stability of the expressed protein from the hybrid sequence, and their uses. The invention also concerns plasmids and yeast strains capable of being used in said methods.