Costantini Maria, Bernardi Giorgio
Laboratory of Molecular Evolution, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.
Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13971-6. doi: 10.1073/pnas.0803916105. Epub 2008 Sep 9.
The human genome, a typical mammalian genome, is made up of long (approximately 1-Mb, on average) regions, the isochores, that are fairly homogeneous in base composition and belong in five families characterized by different GC levels. An analysis of di- and tri-nucleotide densities in the isochores from the five families has shown large differences. These different "short-sequence designs:" (i) account for the fractionation of human DNA (and vertebrate DNA in general) when using sequence-specific ligands in density gradients, (ii) are very similar in whole isochores and in the corresponding intergenic sequences and introns, (iii) are reflected in different codon usages, (iv) lead to amino acid differences that increase the thermal stability of the proteins encoded by genes located in increasingly GC-rich isochore families, and (v) correspond to different chromatin structures.
人类基因组作为典型的哺乳动物基因组，由长片段（平均约1兆碱基）组成，即等密度区，其碱基组成相当均匀，可分为五个以不同GC含量为特征的家族。对这五个家族等密度区中二核苷酸和三核苷酸密度的分析显示出很大差异。这些不同的“短序列设计”：（i）在密度梯度中使用序列特异性配体时，解释了人类DNA（以及一般脊椎动物DNA）的分级分离现象；（ii）在整个等密度区以及相应的基因间序列和内含子中非常相似；（iii）反映在不同的密码子使用上；（iv）导致氨基酸差异，从而增加了位于GC含量越来越高的等密度区家族中的基因所编码蛋白质的热稳定性；（v）对应于不同的染色质结构。
