Nilsson Daniel, Andersson Björn
Center for Genomics and Bioinformatics, Karolinska Institutet, Berzeliusv. 35, SE-171 77 Stockholm, Sweden.
Exp Parasitol. 2005 Mar;109(3):143-9. doi: 10.1016/j.exppara.2004.12.004.
The genome organization of kinetoplastid parasites is unusual, with chromosomes containing several long regions of polycistronically transcribed genes. The regions where the direction of transcription switches have been hypothesized to contain origins of replication and possibly also centromers and promoters. We report that overall strand asymmetry patterns can be observed in Trypanosoma cruzi and Trypanosoma brucei with optima on strand-switch regions. The base skews of T. cruzi and T. brucei divergent strand-switches show patterns analogous to those for bacterial origins of replication, but they differ from those of Leishmania major. Bias in codon usage and the trypanosomatid unidirectional gene clusters predict most of this skew, but fail to properly explain the same trend in intergenic regions, as does the current knowledge of regulatory sequences.
动基体寄生虫的基因组组织方式不同寻常，其染色体包含几个多顺反子转录基因的长区域。转录方向发生切换的区域被推测含有复制起点，可能还含有着丝粒和启动子。我们报告称，在克氏锥虫和布氏锥虫中可以观察到总体链不对称模式，在链切换区域最为明显。克氏锥虫和布氏锥虫不同链切换的碱基偏斜显示出与细菌复制起点类似的模式，但与硕大利什曼原虫的模式不同。密码子使用偏好和锥虫单向基因簇预测了大部分这种偏斜，但正如目前对调控序列的了解一样，它们未能恰当地解释基因间区域的相同趋势。
