Doolittle R F, Feng D F, Johnson M S, McClure M A
Center for Molecular Genetics, University of California, San Diego, La Jolla 92093.
Q Rev Biol. 1989 Mar;64(1):1-30. doi: 10.1086/416128.
As is the case for some other RNA viruses, the amino acid sequences of retroviral proteins change at an astonishing rate. For example, the proteases of the human immunodeficiency virus (HIV) and the visna lentivirus with which it is often compared are as different as the proteases of fungi and mammals, and those of the human type I leukemia virus are as different from HIV or visna as are the proteins of humans and bacteria. That the sequences of retrovirus proteins can be recognized as sharing common ancestry with non-retroviral proteins implies that the vastly accelerated change has begun only recently or occurs very sporadically. Only a scheme whereby exogenous retroviruses exist as short-lived bursts upon a backdrop of germline-encoded endogenous viruses is consistent with the sequence data. Retroviruses are related to many other reverse transcriptase-bearing entities present in the genomes of eukaryotes. They also have proteins that are homologous with those of some plant and animal DNA viruses, and their reverse transcriptase is recognizably similar to sequences found in the introns of some fungal mitochondria. Computer alignment of all these sequences allows an overall phylogeny to be constructed that chronicles the history of events leading to infectious retroviruses.
与其他一些RNA病毒的情况一样,逆转录病毒蛋白的氨基酸序列以惊人的速度发生变化。例如,人类免疫缺陷病毒(HIV)的蛋白酶与常与之比较的维斯纳慢病毒的蛋白酶,其差异程度如同真菌和哺乳动物的蛋白酶之间的差异;而人类I型白血病病毒的蛋白酶与HIV或维斯纳病毒的蛋白酶的差异,如同人类和细菌的蛋白质之间的差异。逆转录病毒蛋白的序列能够被识别为与非逆转录病毒蛋白具有共同祖先,这意味着这种极大加速的变化只是最近才开始,或者发生得非常零星。只有一种方案与序列数据相符,即外源性逆转录病毒以短暂爆发的形式存在于种系编码的内源性病毒的背景之中。逆转录病毒与真核生物基因组中存在的许多其他携带逆转录酶的实体有关。它们还具有与某些植物和动物DNA病毒的蛋白质同源的蛋白质,并且它们的逆转录酶与在一些真菌线粒体内含子中发现的序列明显相似。对所有这些序列进行计算机比对,可以构建一个总体系统发育树,记录导致感染性逆转录病毒的事件历史。