Conserved subfamilies of the Drosophila HeT-A telomere-specific retrotransposon.
Conserved subfamilies of the Drosophila HeT-A telomere-specific retrotransposon.
复制标题
果蝇 HeT-A 端粒特异性逆转录转座子的保守亚科。
DOI：
10.1093/genetics/148.1.233
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发表时间：
1998
期刊：
影响因子：
3.3
通讯作者：
Pardue,ML
中科院分区：
文献类型：
--
作者：
Danilevskaya,ON;Lowenhaupt,K;Pardue,ML
HeT-A是果蝇端粒的主要成分，是第一个被认为具有重要细胞功能的反转录转座子。与大多数反转录转座子不同，它的基因组有一半以上是非编码的。3′端含有> 2.5kb的非编码序列。HeT-A的拷贝因插入或缺失以及多个核苷酸变化而不同，这最初使我们得出结论，HeT-A非编码序列非常不稳定。然而，我们现在可以报告，在新的序列和进一步的分析的基础上，这些差异中的大多数是由于存在少量的保守序列亚家族，而不是广泛的序列变化在每个转座事件。高水平的序列保守性的亚家族内表明，它们产生于一个小数目的复制活性元件。所有的HeT-A亚家族都保留了两个有趣的特征。首先，在3′端非编码区中，富含A的序列片段形成了一种独特的模式。第二，核苷酸组成有很强的链偏向性：染色体中部5′到3′的DNA链通常富含腺嘌呤，而鸟嘌呤很少。虽然HeT-A 3′非编码序列没有受到编码序列的限制，但它似乎受到其他进化限制，这可能反映了它在端粒中的作用。
HeT-A, a major component of Drosophila telomeres, is the first retrotransposon proposed to have a vital cellular function. Unlike most retrotransposons, more than half of its genome is noncoding. The 3′ end contains >2.5 kb of noncoding sequence. Copies of HeT-A differ by insertions or deletions and multiple nucleotide changes, which initially led us to conclude that HeT-A noncoding sequences are very fluid. However, we can now report, on the basis of new sequences and further analyses, that most of these differences are due to the existence of a small number of conserved sequence subfamilies, not to extensive sequence change during each transposition event. The high level of sequence conservation within subfamilies suggests that they arise from a small number of replicatively active elements. All HeT-A subfamilies show preservation of two intriguing features. First, segments of extremely A-rich sequence form a distinctive pattern within the 3′ noncoding region. Second, there is a strong strand bias of nucleotide composition: The DNA strand running 5′ to 3′ toward the middle of the chromosome is unusually rich in adenine and unusually poor in guanine. Although not faced with the constraints of coding sequences, the HeT-A 3′ noncoding sequence appears to be under other evolutionary constraints, possibly reflecting its roles in the telomeres.