20个物种同义密码子偏性的比较分析

Comparative studies on synonymous codon usage bias in twenty species

对6种双子叶植物、4种单子叶植物、7种多细胞真核动物、2种单细胞真核生物及1种原核生物(大肠杆菌)的编码序列(CodingDNASequence,CDS)进行了比较研究。结果发现,各供试物种密码子的用法存在明显的位置依赖,编码区域不同区段对密码子选择使用的程度差异很大,表明基因的同义密码子偏性与其编码区不同区域的碱基环境密切相关;基因组差异是造成密码子使用偏性的首要因素。对"翻译起始区"和"翻译终止区"的特征分析发现,大部分供试物种编码序列中的"翻译起始区"碱基偏置强烈,"翻译终止区"相对较弱,暗示"翻译起始区"的密码子使用对提高蛋白翻译的效率和精确性更为重要。不同物种中G+C含量对其同义密码子偏性的贡献率差异很大,但并非是影响同义密码子使用偏性的唯一因素。可以认为,基因编码区域密码子偏性的研究能为搜寻物种进化的分子机理提供线索。

A comparison of synonymous codon usage bias was made in twenty species from micro to higher plants and animals which involves six Dicotyledoneae,four Monocotyledones,seven multicellular animals,two unicellular eukaryotes and one prokaryote (Escherichia coli).Results showed that the codon usage was significantly position-dependent.Every species selectively used synonymous codons at different sections in coding region,suggesting that codon usage bias was closely related to CDS base composition environment.In a word,codon usage bias was primarily determined by difference among investigated species.Most species in this study showed significantly stronger variation in codon usage in translational initiation region than that in translational termination region,which suggested that codon usage in translational initiation region was more important for increasing protein-translation efficiency or accuracy.The contribution of G+C content to codon usage bias was extremely changeable in different species,probably according to its base composition,which suggested that G+C content in coding region was only one of important factors in shaping codon usage bias.Studies on codon usage bias in the coding region of genes could give some clues for searching the molecular mechanism how the species evolves.