Arkov A L, Korolev S V, Kisselev L L
Engelhardt Institute of Molecular Biology, Moscow, Russia.
Nucleic Acids Res. 1995 Nov 25;23(22):4712-6. doi: 10.1093/nar/23.22.4712.
The nearest 5' context of 2559 human stop codons was analysed in comparison with the same context of stop-like codons (UGG, UGC, UGU, CGA for UGA; CAA, UAU, UAC for UAA; and UGG, UAU, UAC, CAG for UAG). The non-random distribution of some nucleotides upstream of the stop codons was observed. For instance, uridine is over-represented in position -3 upstream of UAG. Several codons were shown to be over-represented immediately upstream of the stop codons: UUU(Phe), AGC(Ser), and the Lys and Ala codon families before UGA; AAG(Lys), GCG(Ala), and the Ser and Leu codon families before UAA; and UCA(Ser), AUG(Met), and the Phe codon family before UAG. In contrast, the Thr and Gly codon families were under-represented before UGA, while ACC(Thr) and the Gly codon family were under-represented before UAG and UAA respectively. In an earlier study, uridine was shown to be over-represented in position -3 before UGA in Escherichia coli [Arkov,A.L., Korolev,S.V. and Kisselev,L.L. (1993) Nucleic Acids Res., 21,2891-2897]. In that study, the codons for Lys, Phe and Ser were shown to be over-represented immediately upstream of E. coli stop codons. Consequently, E. coli and human termination codons have similar 5' contexts. The present study suggests that the 5' context of stop codons may modulate the efficiency of peptide chain termination and (or) stop codon readthrough in higher eukaryotes, and that the mechanisms of such a modulation in prokaryotes and higher eukaryotes may be very similar.
分析了2559个人类终止密码子最接近的5'侧翼序列，并与类似终止密码子（UGA对应的UGG、UGC、UGU、CGA；UAA对应的CAA、UAU、UAC；UAG对应的UGG、UAU、UAC、CAG）的相同侧翼序列进行比较。观察到终止密码子上游某些核苷酸的非随机分布。例如，尿苷在UAG上游第-3位过度富集。有几个密码子在终止密码子紧邻上游处过度富集：UGA之前的UUU（苯丙氨酸）、AGC（丝氨酸）以及赖氨酸和丙氨酸密码子家族；UAA之前的AAG（赖氨酸）、GCG（丙氨酸）以及丝氨酸和亮氨酸密码子家族；UAG之前的UCA（丝氨酸）、AUG（甲硫氨酸）以及苯丙氨酸密码子家族。相反，苏氨酸和甘氨酸密码子家族在UGA之前出现频率较低，而ACC（苏氨酸）和甘氨酸密码子家族分别在UAG和UAA之前出现频率较低。在早期研究中，尿苷在大肠杆菌中UGA上游第-3位被证明过度富集[Arkov,A.L., Korolev,S.V.和Kisselev,L.L.（1993年）《核酸研究》，21,2891 - 2897]。在该研究中，赖氨酸、苯丙氨酸和丝氨酸的密码子在大肠杆菌终止密码子紧邻上游处被证明过度富集。因此，大肠杆菌和人类的终止密码子具有相似的5'侧翼序列。本研究表明，终止密码子的5'侧翼序列可能调节高等真核生物中肽链终止和（或）终止密码子通读的效率，并且原核生物和高等真核生物中这种调节机制可能非常相似。
