biostudies-literatureHeo JNational Research Foundation of Korea (NRF)1760https://www.ebi.ac.uk/biostudies/studies/S-EPMC12698673biostudies-literatureUnknown8(1)The transcription machinery is assembled via interactions of DNA-bound transcriptional activators and coactivators. When the eukaryotic RNA polymerase II complex is formed, cAMP-regulated transcription factor (CREB) binding protein (CBP) acts as a general coactivator bridging the transcriptional apparatus. Forkhead box protein O4 (FOXO4), a transcription factor, has been reported to bind to the KIX domain of CBP (CBP-KIX). Although the CR3 of FOXO4 (FOXO4-CR3) binds as expected to the MLL and c-Myb sites of CBP-KIX, its substantially higher affinity for CBP, compared to its homolog FOXO3a, cannot be explained by a single conserved ΦXXΦΦ binding motif. Here, we found that a second ΦXXΦΦ motif in FOXO4-CR3 provides an additional point of contact for CBP-KIX. Isothermal titration calorimetry Communications biologyRecognition of two hydrophobic pockets in the KIX domain of CBP by FOXO4 transactivation domain.PMC12698673RS-2024-00440614RS-2024-00411137RS-2025-16068849Ryu KSHeo JPark CJfalseRecognition of two hydrophobic pockets in the KIX domain of CBP by FOXO4 transactivation domain.The transcription machinery is assembled via interactions of DNA-bound transcriptional activators and coactivators. When the eukaryotic RNA polymerase II complex is formed, cAMP-regulated transcription factor (CREB) binding protein (CBP) acts as a general coactivator bridging the transcriptional apparatus. Forkhead box protein O4 (FOXO4), a transcription factor, has been reported to bind to the KIX domain of CBP (CBP-KIX). Although the CR3 of FOXO4 (FOXO4-CR3) binds as expected to the MLL and c-Myb sites of CBP-KIX, its substantially higher affinity for CBP, compared to its homolog FOXO3a, cannot be explained by a single conserved ΦXXΦΦ binding motif. Here, we found that a second ΦXXΦΦ motif in FOXO4-CR3 provides an additional point of contact for CBP-KIX. Isothermal titration calorimetry 2025-01-01T00:00:00Z2025 Dec2026-06-06T02:15:58.011Z2026-05-24T03:12:15.018ZS-EPMC126986734138185010.1038/s42003-025-09146-w