二氢叶酸还原酶缺陷型中华仓鼠卵巢细胞偏爱密码子的研究

目的研究二氢叶酸还原酶缺陷型中华仓鼠卵巢细胞（CHO dhfr-）的偏爱密码子。方法建立CHO dhfr-细胞高丰度mRNA的cDNA文库，对该文库进行签定以获得合格的编码蛋白质的cDNA序列，统计密码子使用频率并与CUTG数据库中的中华仓鼠比较，同时对所获得的cDNA序列进行对应统计分析。结果获得了50个合格的CHO dhfr-细胞高丰度蛋白的cDNA序列，与中华仓鼠密码子使用频率比较，除了Pro，Arg外，其余氨基酸的最高使用频率的密码子在CHO dhfr-细胞和中华仓鼠中都相同。同时根据对应分析确定了能解释最多变量（14．7％）的第一主成分，确定了22个同义密码子为CHO dhfr-细胞偏爱密码子。结论CHO dhfr-细胞存在自身偏爱的密码子，提示密码子的偏爱性是不同哺乳动物细胞功能差异的因素之一，也为外源基因在CHO dhfr-细胞中通过优化密码子而获得高表达提供了新思路。

Codon usage of Chinese hamster ovary cells

Objective To investigate the optimal codons of dihydrofolate reductase (dhfr) minus Chinese hamster ovary cells (CHO dhfr-).Methods A cDNA library of CHO dhfr-containing high abundence mRNA was constructed and protein-coding sequences were obtained after identification and analysis.Codon frequence of CHO dhfr-was compared with that of Chinese hamster in CUTG database.Then codon usage variation among cDNA was investigated using correspondence analysis (COA).Results Fifty qualified cDNAs from CHO dhfr-were selected,which encodes proteins of high abundence.Comparing with the codon frequence of Chinese hamster,the highest frequence of synonymous codons for amino acids in CHO dhfr-cells were the same as Chinese hamster except that of Arg and Pro.This method of COA identifies the first main factor which can account for the largest fractions(14.7%)of variation among cDNAs. Twenty-two synonymous codons were identified as the optimal codons of CHO cell.Conclusion CHO dhfr-cell has its own optimal codons,it is suggested that codon bias is one of reasons for functional diversity of different mammal cells and it is an effective stratagy to modification of the codon usage of the foreign gene according to the optimal codons of CHO dhfr- to increase the production of foreign gene.