THE CONTRIBUTION OF DNA SLIPPAGE TO EUKARYOTIC NUCLEAR 18S-RIBOSOMAL-RNA EVOLUTION
THE CONTRIBUTION OF DNA SLIPPAGE TO EUKARYOTIC NUCLEAR 18S-RIBOSOMAL-RNA EVOLUTION
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DOI：
10.1007/bf00160511
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发表时间：
1995-06-01
影响因子：
3.9
通讯作者：
HANCOCK, JM
中科院分区：
文献类型：
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作者：
HANCOCK, JM
分析的204个真核生物核小亚基核糖体RNA序列中有6个显示出高度显著的短序列基序聚类，这表明在它们最近的进化史中，它们内部固定了复制滑移产物。另外72个序列显示较弱的序列重复迹象。SSU rrna中的重复序列优先位于可变区域，尤其是V4和V7。紧接5′至V7 （C7）的保守区也始终重复。然而可变区域的长度不同，似乎是由滑移产物的固定而进化的，C7没有显示长度变化的迹象。因此，C7中的重复要么不是滑动的结果，要么反映了非常古老的滑动事件。小亚基rnas序列简单性的系统发育分布是不完整的，主要局限于哺乳动物、顶复合体、四膜虫科和锥虫科。与序列简单性相关的分子区域随着分类分组的不同而变化，就像发生滑动的序列基序一样。在疟原虫属的一个谱系中，插入率和取代率的比较证实，可变区域的插入率和取代率都高于保守区域。可变区域的插入率远低于替代率，这表明选择对滑移产物的作用比对这些区域的点突变的作用更强。可变区域之间的共同进化模式可能反映了选择作用于整个基因中滑动衍生序列结合的结果。
Six of 204 eukaryotic nuclear small-subunit ribosomal RNA sequences analyzed show a highly significant degree of clustering of short sequence motifs that indicates the fixation of products of replication slippage within them in their recent evolutionary history. A further 72 sequences show weaker indications of sequence repetition. Repetitive sequences in SSU rRNAs are preferentially located in variable regions and in particular in V4 and V7. The conserved region immediately 5' to V7 (C7) is also consistently repetitive. Whereas variable regions vary in length and appear to have evolved by the fixation of slippage products, C7 shows no indication of length variation. Repetition within C7 is therefore either not a consequence of slippage or reflects very ancient slippage events. The phylogenetic distribution of sequence simplicity in small-subunit rRNAs is patchy, being largely confined to the Mammalia, Apicomplexa, Tetrahymenidae, and Trypanosomatidae. The regions of the molecule associated with sequence simplicity vary with taxonomic grouping as do the sequence motifs undergoing slippage. Comparison of rates of insertion and substitution in a lineage within the genus Plasmodium confirms that both rates are higher in variable regions than in conserved regions. The insertion rate in variable regions is substantially lower than the substitution rate, suggesting that selection acts more strongly on slippage products than on point mutations in these regions. Patterns of coevolution between variable regions may reflect the consequences of selection acting on the incorporation of slippage-derived sequences across the gene.