Supplementary Figure 3: Expression of control baits and autoactivation assay.

(a) LexA control baits used for epitope mapping are expressed in yeast to investigate their correct expression, as done for the screening baits. The only bait that does not carry a HA tag is LexA-Integrase, whose expression is shown, in the central figure, for two different clones (CFUs). (b) Auto-activation assay for screening and control baits. Yeast baits spotted on histidine-lacking plates in which 3-AT is titrated, allow identification of auto-activation level. The 3-AT concentration, at which non-specific growth (in the absence of an interactor) is arrested, is included in the medium when testing an intrabody interaction. H3 screening bait (LexA-H3-Gcn5wt-HA) needs at least 5mM 3AT, while other control baits are grown at 1.25mM 3AT. As for the Integrase bait panel, LexA-IN-P300wt-HA does not show any auto-activation, unlike LexA-P300wt-HA and LexA-IN which require 1.25mM 3AT.