栖热菌噬菌体TSP4密码子偏嗜性及其对基因异源表达的影响

 为了探索噬菌体TSP4、栖热菌模式菌株Thermus thermophilus HB27中6种蛋白编码序列和Escherichia coli基因组遗传密码子使用偏嗜性,探索TSP4基因密码子偏嗜性对其基因异源表达的影响本研究利用生物学软件Editseq和RSCU算法统计噬菌体TSP4密码子使用频率并分析其偏嗜性,与栖热菌HB27的同源基因以及常温菌E.coli基因组的密码子使用偏嗜性进行对比分析.结果显示,噬菌体TSP4与栖热菌HB27优势密码子相似度高达85%,而与E.coli的相似性仅有65%.为了验证分析结果,选取TSP4基因组中一个潜在分子伴侣基因序列在E.coli BL21和E.coli Rosetta(补充了BL21菌株中缺失的6个稀有密码子)中进行异源表达.噬菌体TSP4与其宿主菌HB27之间密码子高相似性说明在长期的进化过程中TSP4在基因水平上形成对宿主的一种适应性机制.异源表达结果显示,分子伴侣基因在E.coli BL21中未见明显表达,但在Rosetta中高效表达,说明Rosetta中补充的 6个稀有密码子明显有助于分子伴侣基因的表达,该结果也进一步证明密码子偏嗜性是否一致在很大程度上影响基因的表达.

Codon usage bias of Thermus phage TSP4 and its effect on protein heterologous expression

This study is to analyze the codon usage bias of six protein-coding sequences in the genomes of phage TSP4,Thermus thermophilus HB27 and Escherichia coli,and to investigate the effects of codon bias on the heterologous expression of TSP4 genes.Biological software Editseq and algorithm of RSCU were used to analyze the frequency of synonymous codon usage of TSP4 genes to obtain an index of codon usage bias,which was further compared with that of Thermus HB27 and E.coli homologous genes.The results showed that,based on these compared sequences,TSP4 shared 85% similarity of codon usage frequency with Thermus HB27 but only 65% with E.coli.Higher similarity between phage TSP4 and HB27 indicated that TSP4 might possess an adaptation mechanism at the genetic level for its host HB27 during evolution.To test the effects of codon usage bias on the heterologous expression of TSP4 genes,a potential chaperone-coding gene of TSP4 was used for expression in E.coli BL21 and Rosetta(contains six codons rarely used in BL21 strain),respectively.The results showed that protein expression of the target gene was not detected in E.coli BL21 but was observed at a high level in E.coli Rosetta,indicating that the E.coli Rosetta containing six rare codons contributed significantly to the expression of TSP4 chaperone gene,and codon usage bias had a significant effect on gene heterolougs expression.