McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine.
Nucleic Acids Res. 2013 Aug;41(15):7401-19. doi: 10.1093/nar/gkt512. Epub 2013 Jun 9.
LINE1s occupy 17% of the human genome and are its only active autonomous mobile DNA. L1s are also responsible for genomic insertion of processed pseudogenes and >1 million non-autonomous retrotransposons (Alus and SVAs). These elements have significant effects on gene organization and expression. Despite the importance of retrotransposons for genome evolution, much about their biology remains unknown, including cellular factors involved in the complex processes of retrotransposition and forming and transporting L1 ribonucleoprotein particles. By co-immunoprecipitation of tagged L1 constructs and mass spectrometry, we identified proteins associated with the L1 ORF1 protein and its ribonucleoprotein. These include RNA transport proteins, gene expression regulators, post-translational modifiers, helicases and splicing factors. Many cellular proteins co-localize with L1 ORF1 protein in cytoplasmic granules. We also assayed the effects of these proteins on cell culture retrotransposition and found strong inhibiting proteins, including some that control HIV and other retroviruses. These data suggest candidate cofactors that interact with the L1 to modulate its activity and increase our understanding of the means by which the cell coexists with these genomic 'parasites'.
LINE1 占据了人类基因组的 17%，是其唯一活跃的自主移动 DNA。L1 还负责基因组中加工假基因和超过 100 万个非自主逆转录转座子（Alu 和 SVA）的插入。这些元素对基因组织和表达有重大影响。尽管逆转录转座子对基因组进化很重要，但它们的生物学特性仍有许多未知之处，包括参与逆转录转座、形成和运输 L1 核糖核蛋白颗粒等复杂过程的细胞因子。通过标记 L1 构建体的共免疫沉淀和质谱分析，我们鉴定出与 L1 ORF1 蛋白及其核糖核蛋白相关的蛋白质。这些蛋白质包括 RNA 转运蛋白、基因表达调节剂、翻译后修饰酶、解旋酶和剪接因子。许多细胞蛋白与 L1 ORF1 蛋白在细胞质颗粒中共定位。我们还检测了这些蛋白质对细胞培养逆转录转座的影响，发现了一些具有强烈抑制作用的蛋白质，包括一些控制 HIV 和其他逆转录病毒的蛋白质。这些数据表明候选共因子与 L1 相互作用，调节其活性，并增加我们对细胞与这些基因组“寄生虫”共存方式的理解。
