Long interspersed nuclear elements 1 (LINE1) are non-LTR retrotransposons that represent the greatest remodeling force of the human genome during evolution. Genomically, LINE1 are constituted by a 5´ untranslated region (UTR), where the promoter regions are located, three open reading frames (ORF0, ORF1, and ORF2) and one 3´UTR, which has a poly(A) tail that harbors the short interspersed nuclear elements (SINEs) Alu and SVA. Although the intrinsic nature of LINE1 is to be copied and inserted into the genome, an increase in their mobility produces genomic instability. In response to this, the cell has “designed” many mechanisms controlling the retrotransposition levels of LINE1; however, alterations in these regulation systems can increase LINE1 mobility and the formation of chimeric genes. Evidence indicates that 988 human genes have LINE1 inserted in their sequence, resulting in the transcriptional control of genes by their own promoters, as well as by the LINE1 antisense promoter (ASP). To date, very little is known about the biologic impact of this and the L1-MET chimera is a more or less studied case. ASP hypomethylation has been observed in all studied cancer types, leading to increased L1-MET expression. In specific types of cancer, this L1-MET increase controls both low and high MET protein levels. It remains to be clarified if this protein product is a chimeric protein.

长散布的核元件1（LINE1）是非LTR反转录转座子，代表人类基因组在进化过程中的最大重塑力。从基因组上讲，LINE1由启动子区域所在的5´非翻译区（UTR），三个开放阅读框（ORF0，ORF1和ORF2）和一个3´UTR组成，该3´UTR具有多聚（A）尾巴短散布的核元素（SINE）Alu和SVA。尽管LINE1的内在本质将被复制并插入基因组，但其迁移率的增加会导致基因组不稳定。响应于此，细胞已经“设计”了许多机制来控制LINE1的逆转座位；但是，这些调控系统的改变会增加LINE1的移动性和嵌合基因的形成。有证据表明，988个人类基因的序列中插入了LINE1，从而导致基因通过其自身的启动子以及LINE1反义启动子（ASP）进行转录控制。迄今为止，人们对这种生物和生物的生物学影响知之甚少。L1-MET嵌合体或多或少是研究案例。在所有研究的癌症类型中均观察到ASP低甲基化，从而导致L1-MET表达增加。在特定类型的癌症中，这种L1-MET升高可控制低和高MET蛋白水平。该蛋白产物是否为嵌合蛋白尚待阐明。