Mager D L, Freeman J D
Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada.
Virology. 1995 Nov 10;213(2):395-404. doi: 10.1006/viro.1995.0012.
The evolutionary origin and age of the HERV-H family of human endogenous retrovirus-like sequences was investigated in this study. HERV-H elements exist in approximately 900 partially deleted copies and 50-100 more intact forms in humans and Old World monkeys. However, their possible presence in more divergent species is unknown. We have isolated a 1.6-kb genomic DNA segment from the New World monkey marmoset that had been PCR amplified using human HERV-H primers. DNA and protein comparisons and database searches indicate that this marmoset clone is more closely related to human HERV-H elements than to any other sequence, indicating that HERV-H-related sequences do exist in New World monkeys. In contrast to the high copy numbers of deleted elements in Old World primates. Southern blot analysis shows that such elements are present in less than 50 copies in two different species of New World monkey. To estimate evolutionary ages of the common deleted form of the element, a selected DNA segment from the pol region was compared from multiple human HERV-H elements. This comparison suggests that many HERV-H elements of the abundant deleted subfamily integrated approximately 30-35 million years ago. Very similar percentage divergence values between 5' and 3' long terminal repeats of individual elements of the deleted subfamily also suggest that these elements are close in age. These results indicate that HERV-H elements first appeared in the germline prior to the New World/Old World divergence over 40 million years ago. Interestingly, they remained in low numbers in the New World branch while a subfamily underwent a major amplification in Old World primates before the time of divergence of hominoids from Old World monkeys.
本研究调查了人类内源性逆转录病毒样序列的HERV-H家族的进化起源和年代。HERV-H元件在人类和旧世界猴中以大约900个部分缺失拷贝和50 - 100个更完整的形式存在。然而，它们在更具分化的物种中是否可能存在尚不清楚。我们从新世界猴狨猴中分离出一个1.6kb的基因组DNA片段，该片段是使用人类HERV-H引物进行PCR扩增得到的。DNA和蛋白质比较以及数据库搜索表明，这个狨猴克隆与人类HERV-H元件的关系比与任何其他序列的关系更密切，这表明HERV-H相关序列确实存在于新世界猴中。与旧世界灵长类动物中大量缺失元件的高拷贝数形成对比。Southern印迹分析表明，在两种不同的新世界猴物种中，此类元件的拷贝数少于50个。为了估计该元件常见缺失形式的进化年代，从多个人类HERV-H元件中比较了pol区域的一个选定DNA片段。这种比较表明许多丰富的缺失亚家族的HERV-H元件大约在3000万至3500万年前整合。缺失亚家族单个元件的5'和3'长末端重复序列之间非常相似的百分比差异值也表明这些元件的年代相近。这些结果表明，HERV-H元件在4000多万年前新世界/旧世界分化之前首次出现在种系中。有趣的是，它们在新世界分支中数量一直较少，而一个亚家族在旧世界灵长类动物中在类人猿与旧世界猴分化之前经历了一次主要的扩增。
