Dechering K J, Cuelenaere K, Konings R N, Leunissen J A
Department of Molecular Biology and CAOS/CAMM Center, University of Nijmegen, Toernooiveld 1,6525 ED Nijmegen, The Netherlands.
Nucleic Acids Res. 1998 Sep 1;26(17):4056-62. doi: 10.1093/nar/26.17.4056.
The unusual base composition of the genome of the human malaria parasite Plasmodium falciparum prompted us to systematically investigate the occurrence of homopolymeric DNA tracts in the P. falciparum genome and, for comparison, in the genomes of Homo sapiens , Saccharomyces cerevisiae , Caenorhabditis elegans , Arabidopsis thaliana , Escherichia coli and Mycobacterium tuberculosis. Comparison of theobserved frequencies with the frequencies as expected for random DNA revealed that homopolymeric (dA:dT) tracts occur well above chance in the eukaryotic genome. In the majority of these genomes, (dA:dT) tract overrepresentation proved to be an exponential function of the tract length. (dG:dC) tract overrepresentation was absent or less pronounced in both prokaryotic and eukaryotic genomes. On the basis of our results, we propose that homopolymeric (dA:dT) tracts are expanded via replication slippage. This slippage-mediated expansion does not operate on tracts with lengths below a critical threshold of 7-10 bp.
人类疟原虫恶性疟原虫基因组不同寻常的碱基组成促使我们系统地研究恶性疟原虫基因组中同聚物DNA序列的出现情况，并将其与人类、酿酒酵母、秀丽隐杆线虫、拟南芥、大肠杆菌和结核分枝杆菌基因组进行比较。将观察到的频率与随机DNA预期的频率进行比较后发现，真核生物基因组中同聚物（dA:dT）序列出现的频率远高于偶然概率。在这些基因组中的大多数中，（dA:dT）序列的过度存在被证明是序列长度的指数函数。在原核生物和真核生物基因组中，（dG:dC）序列的过度存在均不存在或不太明显。基于我们的研究结果，我们提出同聚物（dA:dT）序列是通过复制滑动而扩展的。这种滑动介导的扩展作用于长度低于7 - 10个碱基对临界阈值的序列。
