Discovery of high-affinity BCL6-binding peptide and its structure-activity relationship.
B cell lymphoma 6 (BCL6) is a transcriptional repressor that interacts with its corepressors BcoR and SMRT. Since this protein-protein interaction (PPI) induces activation and differentiation of B lymphocytes, BCL6 has been an attractive drug target for potential autoimmune disease treatments. Here we report a novel BCL6 inhibitory peptide, F1324 (Ac-LWYTDIRMSWRVP-OH), which we discovered using phage display technology; we also discuss this peptide's structure-activity relationship (SAR). For BCL6(5-129) binding, KD and IC50 values of F1324 were 0.57 nM and 1 nM according to the results of an SPR analysis and cell-free ELISA assay, respectively. In contrast, BcoR(Arg498-514Pro) and SMRT(Leu1422-Arg1438) exhibited relatively weak micromole-order binding to BCL6. Furthermore, Fusion protein AcGFP-F1324 transiently expressed in HEK293T cells inhibited intracellular PPI in cell-based M2H assay. By examination of the truncation and fragmentation of F1324, the C-terminal sequence WRVP, which is similar to the BcoR(509-512) sequence WVVP, was identified as being critical for BCL6 binding. In addition, subsequent single-crystal X-ray diffraction analysis of F1324/BCL6(5-129) complex revealed that the high affinity of F1324 was caused by effective interaction of its side chains while its main chain structure was similar to that of BcoR(Arg498-514Pro). To our knowledge, F1324 is the strongest BCL6-binding peptide yet reported.
['Sakamoto|Kotaro|K|', 'Sogabe|Satoshi|S|', 'Kamada|Yusuke|Y|', 'Sakai|Nozomu|N|', 'Asano|Kouhei|K|', 'Yoshimatsu|Mie|M|', 'Ida|Kou|K|', 'Imaeda|Yasuhiro|Y|', 'Sakamoto|Jun-Ichi|JI|']
D001665:Binding Sites D004789:Enzyme Activation D004791:Enzyme Inhibitors D010455:Peptides D011485:Protein Binding D051560:Proto-Oncogene Proteins c-bcl-6 D013329:Structure-Activity Relationship
Peptide BCL6 PPI Phage display