Characterization of short H2A Oncohistones in Cancer

摘要 一个新兴的文学机构已经表明，核小体，染色质的基本亚基， 在一系列常见的癌症中是不稳定的。这种不稳定以前被认为是 需要在组蛋白编码基因中发生癌症特异性突变，称为“致癌组蛋白”。我们确定了一个 癌症可以通过上调核小体获得不稳定核小体的新机制， 核小体中毒组蛋白H2 A变体H2A.B.该变体通常仅在睾丸中表达， 在精子中形成独特的染色质环境。我们比较了 H2A.B和H2 A的序列和野生型H2A.B序列中鉴定的癌组蛋白特征， 这表明这是一个现成的癌组蛋白，就在我们的基因组中。符合本 假设，我们确定了50%的弥漫性大B细胞淋巴瘤和5-10%的 许多其他常见的恶性肿瘤，但不是在睾丸外的正常组织。我们还发现了 表达H2 A. B的癌症中的选择性剪接模式，这些变化以前是 在核小体不稳定的背景下报道。最后，我们进行了敲除研究， 发现H2 A. B减少在几种不同的淋巴瘤细胞系中损害癌细胞生长， 这些结果得到了大规模CRISPR研究的支持。总之，这些数据大大扩展了 可能由癌组蛋白生物学驱动的癌症数量。然而， H2A.B与肿瘤发生的关系尚不清楚。本提案将确定H2A.B对 转录组和表观基因组，以发现H2A.B阳性癌症的新漏洞。在aim中 1，我们采用RNA测序来确定基因表达和选择性剪接的变化， 对H2A.B诱导或还原的反应。在aim 2中我们使用染色质分析方法 在Henikoff实验室开发的研究H2A.B表达对表观基因组的影响。在aim 3中 我们使用目标1和目标2的数据来识别H2A.B阳性癌症的脆弱性， 疗效相似但副作用更好蒽环类抗生素阿克拉维汀的研究 效果优于阿霉素。本提案中的实验将阐明H2A.B在以下方面的作用： 癌症和识别新的治疗漏洞。

Abstract An emerging body of literature has shown that nucleosomes, the fundamental subunit of chromatin, are destabilized in a broad array of common cancers. This destabilization was previously thought to require cancer-specific mutations in histone-encoding genes, called “oncohistones”. We identified a new mechanism by which cancers can acquire unstable nucleosomes, through upregulation of the nucleosome-poisoning histone H2A variant H2A.B. This variant is normally expressed in testis only, where it contributes to the unique chromatin environment in sperm. We compared the amino acid sequences of H2A.B and H2A and identified oncohistone features in the wildtype H2A.B sequence, suggesting that this is a readymade oncohistone sitting in our genomes. Consistent with this hypothesis, we identified H2A.B expression in 50% of diffuse large B-cell lymphomas and 5-10% of many other common malignancies but not in normal tissue outside of testis. We also found unique patterns of alternative splicing in H2A.B-expressing cancers, and these changes were previously reported in the context of nucleosome destabilization. Finally, we performed knockdown studies and found that H2A.B reduction impairs cancer cell growth in several different lymphoma cell lines, results that are supported by large-scale CRISPR studies. Together, these data substantially expand the number of cancers that may be driven by oncohistone biology. However, the contribution of H2A.B to oncogenesis is not known. This proposal will identify the effects of H2A.B on the transcriptome and epigenome in order to find new vulnerabilities in H2A.B-positive cancers. In aim 1, we employ RNA sequencing to identify changes in gene expression and alternative splicing in response to induction or reduction of H2A.B. In aim 2 we use chromatin profiling methods developed in the Henikoff lab to study the impact of H2A.B expression on the epigenome. In aim 3 we use data from aims 1 and 2 to identify vulnerabilities in H2A.B-positive cancers including investigation of aclarubicin, an anthracycline with similar efficacy but much more favorable side effect profile than doxorubicin. The experiments in this proposal will elucidate the role of H2A.B in cancer and identify novel therapeutic vulnerabilities.