Expression and biological significance of human endogenous retroviral sequences.
Expression and biological significance of human endogenous retroviral sequences.
复制标题
人内源逆转录病毒序列的表达和生物学意义。
作者：
C. Leib;M. Bachmann;R. Brack;Thomas Werner;Erfle;Ruediger Hehlmann
人类基因组包含多种类似于哺乳动物逆转录病毒的元件。大多数这些序列已被发现与灵长类和鼠类 C 型病毒（BaEV、SSAV/GaLV、MuLV）、鼠类 B 型病毒和 A 型颗粒（MMTV、IAP）或人类 T 细胞嗜淋巴细胞病毒（HTLV）有关。总而言之，人类内源性逆转录病毒和逆转录病毒元件估计至少占人类基因组的 0.1% 至 0.6%。与其他转座元件一样，它们可能通过细胞内转座事件或通过产生重组热点来塑造真核基因组。人类逆转录病毒序列已被证明具有转录活性，特别是在人类胎盘和胚胎组织以及人类肿瘤细胞系中。一些与细胞序列共表达的元件被认为在基因表达的调节中发挥作用。此外，人内源逆转录病毒序列的表达可能具有针对相关外源逆转录病毒的重复感染的保护功能。另一方面，内源性逆转录病毒和逆转录病毒元件代表了可能致病的逆转录病毒基因的细胞库。它们可能通过充当不同染色体之间重组事件的位点而参与染色体畸变。此外，它们可以充当插入诱变剂并激活或灭活细胞基因。逆转录病毒基因产物本身也可能具有致病性，p15E 包膜蛋白的免疫抑制作用已表明这一点。因此，人类内源性逆转录病毒和逆转录病毒序列在生物过程中的作用是目前人们非常感兴趣的课题。
The human genome contains a variety of elements resembling mammalian retroviruses. Most of these sequences have been found to be related to primate and murine C-type viruses (BaEV, SSAV/GaLV, MuLV), murine B-type viruses and A-type particles (MMTV, IAP), or human T-cell lymphotropic viruses (HTLV). Altogether, human endogenous retroviruses and retroviral elements are estimated to comprise at least 0.1 to 0.6% of the human genome. Like other transposable elements they may contribute in shaping the eukaryotic genome by intracellular transposition events or by generating hot spots of recombination. Human retroviral sequences have been shown to be transcriptionally active, especially in human placenta and embryonic tissue and in human tumor cell lines. Some elements that are coexpressed with cellular sequences are supposed to play a role in regulation of gene expression. Furthermore, expression of human endogenous retroviral sequences may have a protective function against superinfection by related exogenous retroviruses. On the other hand, endogenous retroviruses and retroviral elements represent a cellular reservoir of possibly pathogenic retroviral genes. They may be involved in chromosomal aberrations by acting as sites for recombination events between different chromosomes. Furthermore, they can act as insertion mutagens and activate or inactivate cellular genes. Retroviral gene products themselves may also be pathogenic as has been shown for the immunosuppressive effects of p15E envelope proteins. Therefore, the role of human endogenous retroviruses and retroviral sequences in biological processes is currently a subject of great interest.