Characterization of short H2A Oncohistones in Cancer

摘要 一批新兴的文献表明，核小体，染色质的基本亚单位， 在一系列常见的癌症中是不稳定的。这种不稳定之前被认为是 需要在组蛋白编码基因中发生癌症特异性突变，称为“癌组织蛋白”。我们确定了一个 癌症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H_2A变异体H_2A.B。该变异体通常只在睾丸中表达， 在那里，它有助于精子中独特的染色质环境。我们比较了氨基酸 H_2A.B和H_2A的序列以及在野生型H_2A_B序列中鉴定的癌组蛋白特征， 这表明这是一种存在于我们基因组中的现成癌组蛋白。与此一致 假设，我们发现50%的弥漫性大B细胞淋巴瘤和5%-10%的弥漫性大B细胞淋巴瘤中有H2A.B的表达 许多其他常见的恶性肿瘤，但不发生在睾丸以外的正常组织中。我们还发现了独特的 在表达H2A.B的癌症中的选择性剪接模式，这些变化以前是 在核小体不稳定的情况下报告的。最后，我们进行了击倒研究， 发现在几种不同的淋巴瘤细胞系中，H2A.B的减少会损害癌细胞的生长， 这些结果得到了大规模CRISPR研究的支持。总而言之，这些数据大大扩展了 可能由癌组蛋白生物学驱动的癌症的数量。然而，中国的贡献 H_2A.B对肿瘤发生的影响尚不清楚。这项提案将确定H_2A.B对 转录组和表观基因组，以便在H2A.B阳性癌症中发现新的脆弱性。在AIM 1，我们使用RNA测序来确定基因表达和选择性剪接的变化 对过氧化氢诱导或还原的反应。在目标2中，我们使用染色质分析方法 由Henikoff实验室开发，用于研究H2A.B表达对表观基因组的影响。在AIM 3中 我们使用AIMS 1和AIMS 2的数据来识别H2A.B阳性癌症的易感性，包括 一种疗效相近但副作用大得多的蒽环类药物阿克拉阿霉素的研究 比阿霉素的效果更好。该方案中的实验将阐明H_2A.B在 癌症，并确定新的治疗脆弱性。

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.