title: Discovery of high-affinity BCL6-binding peptide and its structure-activity relationship.
abstract: 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, KDand IC50values 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.
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan. Electronic address: koutarou.sakamoto@takeda.com.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Sakamoto
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sogabe
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kamada
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Sakai
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Asano
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Mie
authors.initials: M
authors.lastname: Yoshimatsu
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Kou
authors.initials: K
authors.lastname: Ida
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Imaeda
authors.affiliation: Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555, Japan.
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Sakamoto
mesh_terms: D001665:Binding Sites; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D051560:Proto-Oncogene Proteins c-bcl-6 / Q000737:chemistry* / Q000648:ultrastructure*; D013329:Structure-Activity Relationship
chemical_list: C084103:BCL6 protein, human; D004791:Enzyme Inhibitors; D010455:Peptides; D051560:Proto-Oncogene Proteins c-bcl-6
keywords: BCL6; PPI; Peptide; Phage display