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Abstract：
Long Interspersed Element-1 (LINE-1 or L1) are transposable elements similar to retroviruses that have existed in the genome of primates for millions of years. They encode two Open Reading Frame (ORF) proteins (ORF1p and ORF2p) that bind L1 RNA to form a ribonucleoprotein (RNP) complex and are required for L1 integration into the host genome. Humans have evolved with L1 and found ways to limit L1 activity. To identify partners of the L1 RNP, previous studies used ectopic expression of L1 ORF1/2p or RNA in various cancer cells, which express low levels of the ORF proteins. Whether naturally occurring L1 RNP interacts with the same proteins in non-cancer cells is unknown. Here, the aim is to examine the natural assembly of endogenous L1 RNPs in normal human cells. L1 elements are expressed in human embryonic stem cells (hESCs), derived from pre-implantation embryos. Therefore, these cells are used to immunoprecipitate ORF1p followed by MS to identify proteins that associate with the naturally-occurring L1 ORF1p. Some of the same proteins as well as unique proteins are found interacting with the endogenous L1 ORF1p complexes. The analysis of ORF1p-associated proteins in hESCs can help address important questions in both retrotransposon biology and the biology of hESCs.
摘要：
长散布元件-1(LINE-1或L1)是类似于在灵长类动物基因组中存在数百万年的逆转录病毒的转座元件。它们编码两种开放阅读框架（ORF）蛋白（ORF1p和ORF2p），它们结合L1RNA形成核糖核蛋白（RNP）复合物，并且是L1整合到宿主基因组中所必需的。人类已经进化了L1，并找到了限制L1活动的方法。要确定L1RNP的合作伙伴，以前的研究使用L1ORF1/2p或RNA在各种癌细胞中的异位表达，表达低水平的ORF蛋白。天然存在的L1RNP是否与非癌细胞中的相同蛋白质相互作用是未知的。这里,目的是检查正常人细胞中内源性L1RNPs的自然组装。L1元件在人胚胎干细胞（hESC）中表达，来自植入前胚胎。因此,这些细胞用于免疫沉淀ORF1p，然后MS以鉴定与天然存在的L1ORF1p相关的蛋白质。发现一些相同的蛋白质以及独特的蛋白质与内源性L1ORF1p复合物相互作用。hESC中ORF1p相关蛋白的分析可以帮助解决逆转录转座子生物学和hESC生物学中的重要问题。
