古菌起始密码子上游AUG和UAA三联体的频率分布

Frequency Distributions of Triplets AUG and UAA in the Upstream of Start Codons in Archaeal Genomes

分析了三联体AUG和UAA(包括UAG和UGA)在古菌基因组起始密码子上游序列的三个阅读框中的频率分布.在阅读框1,三联体AUG在起始密码子上游有非常明显的缺失.与AUG的缺失相反,三联体UAA的频率在起始密码子上游显著增加.与细菌和真核生物基因组比较发现,古菌基因组的上述特征与细菌十分相似.在古菌基因组起始密码子上游序列中,三联体AUG的缺失和UAA频率的增加可以有效地避免古菌基因被错误的翻译起始,提高翻译效率.

The frequency distributions of triplets AUG and UAA （including UAG and UGA） in 3 reading frames of the upstream sequences of start codons in archaeal genomes are analyzed. The frequency distributions of triplet AUG in reading frame 1 show a significant depletion near the start codon compared with the distributions in reading frames 2 and 3. Contrary to the depletion of AUG, the frequency of triplet UAA in frame 1 increases obviously near the start codon. These distribution characters are consistent with those in bacteria, but different from those in eukaryotes. It is assumed that these special distributions of AUG and UAA in archaea are one of the mechanisms to keep protein coding genes away from incorrect translation initiation and to improve the translation efficiency.