Over-representation of Chi sequences caused by di-codon increase in Escherichia coli K-12.
Over-representation of Chi sequences caused by di-codon increase in Escherichia coli K-12.
复制标题
大肠杆菌 K-12 中双密码子增加导致 Chi 序列过度表达。
DOI：
10.1016/j.gene.2006.05.013
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发表时间：
2006
期刊：
影响因子：
3.5
通讯作者：
M. Tomita
中科院分区：
文献类型：
--
作者：
R. Uno;Y. Nakayama;M. Tomita
Chi序列（5′-GCTGGTGG-3′）是顺式作用的8 bp序列元件，其增强大肠杆菌中由RecBCD途径促进的同源重组。E. coli K-12 MG 1655含有1009个Chi序列，并且该频率远远超过在该大小的基因组中出现8bp序列的预期值。一般认为，Chi序列的过度表达表明它们在进化过程中被选择，因为它们在重组中的功能。3个E.大肠杆菌K-12、O-157和CFT可分为3类（岛型、与其它大肠杆菌相匹配型）。coli和骨架）。岛基因与骨架基因相比具有不同的碱基组成和密码子使用，因此它们相对较新，尚未适应受体基因组典型的碱基组成模式和密码子使用。通过比较Chi频率和岛基因与骨架基因之间的密码子频率来检查Chi序列的过度代表性。主链基因和岛基因之间CTGGTG双密码子频率的差异与Chi序列的频率相关，Chi序列翻译成Leu-Val（-G| CTG| GTG| G-）K-12菌株中的阅读框架。这些结果表明，Chi序列的主阅读框增加是由于双密码子CTG-GTG在全基因组压力下增加以适应E.大肠杆菌K-12菌株的重组酶，并且RecBCD重组酶可能将其识别序列调整为常见的寡聚体，如G-CTG-GTG-G。
Chi sequences (5′-GCTGGTGG-3′) are cis-acting 8 bp sequence elements that enhance homologous recombination promoted by the RecBCD pathway in Escherichia coli. The genome of E. coli K-12 MG1655 contains 1009 Chi sequences and this frequency far exceeds the expected value for occurrence of an 8 bp sequence in a genome of this size. It is generally thought that the over-representation of Chi sequences indicates that they have been selected for during evolution because of their function in recombination. The genes from three E. coli strains (K-12, O157 and CFT) were classified into three categories (island, match to other E. coli, and backbone). Island genes have a different base composition and codon usage in comparison with those in the backbone genes, therefore they were relatively new and not yet adapted to the base composition patterns and codon usage typical of the recipient genome. The over-representation of Chi sequences was examined by comparing Chi frequencies and codon frequencies between island and backbone genes. The difference in the CTGGTG di-codon frequency between the backbone and island genes was correlated with the frequency of Chi sequences which were translated in the Leu-Val (-G|CTG|GTG|G-) reading frame in the K-12 strain. These results suggest that the main reading frame of Chi sequences increased as a result of the di-codon CTG-GTG increasing under a genome-wide pressure for adapting to the codon usage and base composition of the E. coli K-12 strain, and that the RecBCD recombinase might adjust its recognition sequence to a frequently occurring oligomer such as G-CTG-GTG-G.
影响因子：
14.9
作者：
SHARP, PM;LI, WH
通讯作者：
LI, WH
影响因子：
13.8
作者：
Kowalczykowski, SC
通讯作者：
Kowalczykowski, SC
影响因子：
14.9
作者：
SHARP, PM;LI, WH
通讯作者：
LI, WH