Histone acetylation mediated by Brd1 is crucial for Cd8 gene activation during early thymocyte development

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During T-cell development, Cd8 expression is controlled via dynamic regulation of its cis-regulatory enhancer elements. Insufficiency of enhancer activity causes variegated Cd8 expression in CD4+CD8+ double-positive (DP) thymocytes. Brd1 is a subunit of the Hbo1 histone acetyltransferase (HAT) complex responsible for acetylation of histone H3 at lysine 14 (H3K14). Here we show that deletion of Brd1 in haematopoietic progenitors causes variegated expression of Cd8, resulting in the appearance of CD4+CD8TCRβ−/low thymocytes indistinguishable from DP thymocytes in their properties. Biochemical analysis confirms that Brd1 forms a HAT complex with Hbo1 in thymocytes. ChIP analysis demonstrates that Brd1 localizes at the known enhancers in the Cd8 genes and is responsible for acetylation at H3K14. These findings indicate that the Brd1-mediated HAT activity is crucial for efficient activation of Cd8 expression via acetylation at H3K14, which serves as an epigenetic mark that promotes the recruitment of transcription machinery to the Cd8 enhancers.

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Figure 1: Deregulated T-cell development in the Brd1-deficient thymus.
Figure 2: Cell autonomous defect of T cells in the absence of Brd1.
Figure 3: Inefficient activation of Cd8 genes in Brd1-deficient DP thymocytes.
Figure 4: In vitro differentiation of Brd1Δ/Δ DN3 cells.
Figure 5: Impaired CD8 expression in IEL subsets in the absence of Brd1.
Figure 6: Brd1-Hbo1 complex acetylates H3K14 at the Cd8 gene loci.
Figure 7: In vitro differentiation of Brd1Δ/Δ DN3 cells.


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We thank Dr Motomi Osato for providing the human RUNX1 and RUNX3 cDNAs and George R Wendt and Ola Mohammed Kamel Rizq for critical reading of the manuscript. This work was supported in part by Grants-in-aid for Scientific Research (#24249054) and Scientific Research on Innovative Areas ‘Stem Cell Aging and Disease’ (#25115002), ‘Cancer Stem Cell’ (#25130702) and ‘Genome Science’ (#221S0002) from MEXT, Japan, a Grant-in-aid for Core Research for Evolutional Science and Technology (CREST) from the Japan Science and Technology Corporation (JST), and grants from the Takeda Science Foundation and the Uehara Memorial Foundation.

Author information

Y.M., C.W., S.M., A.S. and I.T. designed and performed experiments, analysed data and wrote the manuscript; H.H., M.M.-K., Y.N.-T, G.S. and S.K. designed and performed experiments and provided intellectual input; M.N., A.O., T. Nakayama, D.G.T. and N.Y. provided intellectual input on experimental design and interpretation of results; T. Naito, T.I. and H.K. provided key reagents and assistance with experimental design and interpretation; A.I. led the investigation, devised the project and wrote the manuscript. All authors reviewed and edited the manuscript.

Correspondence to Atsushi Iwama.

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