Histone Extraction and VP22 Quantification

LMH cells transfected with the mutant VP22 constructs were harvested 24 or 48h post-transfection and salt extraction of histones from chromatin was performed as previously described [18 (link),45 (link)]. The proteins included in the extraction fraction were separated in a 10% SDS-PAGE gel and revealed with colloidal Coomassie blue staining. Images of the gels were captured with the Fusion-FX7 imaging system (Vilber Lourmat, Marne-la-Vallée, France) and the level of VP22 proteins found in the histone extract was estimated using the Bio-profil 1D++ software (ChemiSmart 5000) as a ratio of VP22 signal relative to total protein input (for each lane).