Regulation of gene expression by HDAC3

摘要 多能祖细胞向T细胞的分化需要转录因子之间复杂的相互作用。 胸腺细胞在发育的每个阶段都是调节因子。基因表达是通过 调节转录激活和染色质可及性。组蛋白去乙酰化酶（HDAC）限制染色质 可访问性和转录。DP胸腺细胞共表达所有18个HDAC家族成员，但是否共表达 表达的HDAC具有特定的或重叠的功能还没有很好地理解。我们的工作证明了 HDAC3在T细胞发育中具有独特的作用，这不能被任何其他共表达的 HDAC家族成员HDAC3是DP存活和阳性选择所必需的。CD2-icre HDAC3 cKO小鼠 DP胸腺细胞数量减少，胸腺细胞阳性选择严重受阻，导致很少 产生SP胸腺细胞。从机制上讲，CD2-icre HDAC3 cKO小鼠中阳性选择的阻断是由于 一个基因ROR γ t的下调失败。类似地，需要HDAC3来抑制 P2RX7表达增加导致DP胸腺细胞中的嘌呤能受体P2RX7缺陷， CD2-icre HDAC3 cKO小鼠的存活率。HDAC3需要抑制基因的过早表达， 对CD8谱系的承诺。基因表达和H3K27或H3K9组蛋白乙酰化的变化， 在HDAC3缺陷型DP胸腺细胞中，其表达受限制，而非全局性。表达正常的基因 仅限于其他（非T）造血谱系在HDAC 3缺乏时保持关闭， 基因在WT和HDAC3缺陷型DP胸腺细胞之间以相似的水平表达。HDAC3 不是基因调控的通用修饰剂。相反，HDAC3在一小部分 对DP存活、阳性选择和CD4/CD8谱系选择至关重要的基因。的重点 一个建议是确定HDAC3是如何被招募到DP胸腺细胞中的那些基因中的，染色质的改变， 其伴随HDAC3募集和对HDAC3功能至关重要的结合配偶体。

Abstract Differentiation of multi-potent progenitors into T cells requires an intricate interplay between transcriptional regulators as thymocytes proceed through each stage of development. Gene expression is controlled through regulating transcriptional activation and chromatin accessibility. Histone deacetylases (HDACs) limit chromatin accessibility and transcription. DP thymocytes co-express all 18 HDAC family members, but whether co- expressed HDACs have specific or overlapping functions is not well understood. Our work has demonstrated that HDAC3 has a unique role in T cell development, which is not compensated for by any other co-expressed HDAC family member. HDAC3 is required for DP survival and positive selection. CD2-icre HDAC3 cKO mice have decreased numbers of DP thymocytes with a severe block in thymocyte positive selection resulting in few SP thymocytes produced. Mechanistically, the block in positive selection in CD2-icre HDAC3 cKO mice is due to a failure to downregulate a single gene, RORγt. Similarly, HDAC3 is required to suppress expression of the purinergic receptor P2RX7 in DP thymocytes, and increased P2RX7 expression contributes to the defect in DP survival in CD2-icre HDAC3 cKO mice. HDAC3 is required to inhibit premature expression of genes that direct commitment to the CD8 lineage. Changes in gene expression and H3K27 or H3K9 histone acetylation were restricted, rather than global, in HDAC3-deficient DP thymocytes. Genes whose expression is normally restricted to other (non-T) hematopoietic lineages remain off in the absence of HDAC3, and housekeeping genes are expressed at similar levels between WT and HDAC3-deficient DP thymocytes. Therefore, HDAC3 is not a generic or general modifier of gene regulation. Instead, HDAC3 has specific functions in a small set of genes that are critical for DP survival, positive selection and CD4/CD8 lineage choice. The focus of this proposal is to define how HDAC3 is recruited to those genes in DP thymocytes, the alterations in chromatin which accompany HDAC3 recruitment and the binding partners critical for HDAC3 function.