Interaction of proteins is central to various cellular processes like cell growth, proliferation, differentiation and programmed cell death. To study the specific role of a single protein-protein interaction of a multifunctional protein or protein complex, it is necessary to interrupt each single interaction individually to elucidate their respective role and influence they exert. In this study two approaches were employed to modulate protein interactions. First one was to target a known protein-protein interaction by expressing specific peptides in vivo. The second one was based on the LXXLL motif to disrupt interactions between transcription factors and coactivators.