Abstract 5639: TIP60-independent mechanism of BRD8 is involved in colorectal tumorigenesis

Abstract Modifications of histone tails control chromatin structure, and the acetylation is generally associated with euchromatin and transcriptional activation. Acetylated lysine residues are recognized by bromodomains, which serve as acetyl-lysine binding modules and participate in transcriptional regulation. Bromodomain-containing protein 8 (BRD8) is a subunit of the NuA4/TIP60-histone acetyltransferase complex. Although BRD8 has been considered to act as a co-activator of the complex, its biological role remains to be unclear. In this study, we revealed that BRD8 accumulates in colorectal cancer cells through the inhibition of ubiquitin-dependent protein degradation by the interaction with MRG domain binding protein (MRGBP). RNA-seq analysis coupled with genome-wide mapping of BRD8-binding sites disclosed that BRD8 transactivates a set of genes independently of TIP60, a catalytic subunit of NuA4 complex, and that BRD8 regulates the expression of multiple subunits of the pre-replicative complex (pre-RC) in concert with the activator protein-1 (AP-1) transcription factor. Depletion of BRD8 induced cell-cycle arrest at the G1 phase and suppressed proliferation of colorectal cancer cells. We have also shown that the bromodomain of BRD8 is indispensable for not only the interaction with histone H4 or transcriptional regulation but also its own protein stability. These findings provide a new insight into the roles played by BRD8 in human colorectal carcinogenesis and will contribute to the development of new chemotherapeutic agents targeting the bromodomain of BRD8. Citation Format: Kiyoshi Yamaguchi, Saya Nakagawa, Rui Yamaguchi, Paul Sheridan, Kiyoko Takane, Tsuneo Ikenoue, Satoru Nagatoishi, Hiroko Kozuka-Hata, Masaaki Oyama, Susumu Aikou, Yuka Ahiko, Dai Shida, Kouhei Tsumoto, Satoru Miyano, Seiya Imoto, Yoichi Furukawa. TIP60-independent mechanism of BRD8 is involved in colorectal tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5639.