The orientation bias of Chi sequences is a general tendency of G-rich oligomers.
The orientation bias of Chi sequences is a general tendency of G-rich oligomers.
复制标题
Chi序列的方向偏差是富含G的寡聚物的普遍趋势。
DOI：
10.1016/s0378-1119(00)00430-3
复制
发表时间：
2000
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;K. Arakawa;M. Tomita
Chi序列是通过同源重组刺激DNA修复的特异性寡聚体，并且在每个生物体中是不同的序列。大肠杆菌Chi序列（5′-GCTGGTGG-3′）约有75%的拷贝位于前导链上，这种取向偏差通常被认为是Chi序列作为RecBCD途径的信号序列在DNA复制中的生物学作用的结果。然而，我们的计算机分析发现，许多富含G的低聚物也显示出这种不对称的取向模式。Chi方向偏差的转变出现在复制起点和终点周围，但这些位置也与GC含量或GC偏差的转变点一致。我们对枯草芽孢杆菌的基因组进行了同样的分析，发现除了Chi之外，其他富含G的寡聚体也显示出类似的不对称取向模式，其移位点与GC偏斜的移位点一致。然而，流感嗜血杆菌Rd的基因组，其GC偏斜不是那么明显，并没有清楚地显示Chi或其他富含G的寡聚体的不对称取向模式。这些结果使我们认为，Chi方向的不均匀分布在双螺旋的两条链之间主要是由于G含量的不均匀分布（GC偏斜），并且Chi序列的复制相关功能不是导致方向偏差的进化压力的主要因素。
The Chi sequences are specific oligomers that stimulate DNA repair by homologous recombination, and are different sequences in each organism. Approximately 75% of the copies of the Chi sequence (5′-GCTGGTGG-3′) of Escherichia coli reside on the leading strand, and this orientation bias is often believed to be a consequence of the biological role of Chi sequences as the signal sequence of RecBCD pathway in DNA replication. However, our computer analysis found that many G-rich oligomers also show this asymmetric orientation pattern. The shift in the Chi orientation bias appears around the replication origin and terminus, but these locations are also coincident with the shift points in GC content or GC skew. We conducted the same analysis with the genome of Bacillus subtilis, and found that in addition to Chi, other G-rich oligomers show similar asymmetric orientation patterns, whose shift points were coincident with those of the GC skew. However, the genome of Haemophilus influenzae Rd, whose GC skew is not so pronounced, does not clearly show asymmetric orientation patterns of Chi or other G-rich oligomers. These results lead us to suggest that the uneven distribution of the Chi orientation between the two strands of the double helix is mostly due to the uneven distribution of G content (GC skew) and that the replication-related function of Chi sequences is not the primary factor responsible for the evolutionary pressure causing the orientation bias.
DOI：
10.1098/rstb.1995.0003
发表时间：
1995
期刊：
Philosophical transactions of the Royal Society of London. Series B, Biological sciences.
影响因子：
--
作者：
Smith,GR;Amundsen,SK;Dabert,P;Taylor,AF
通讯作者：
Taylor,AF
DOI：
10.1073/pnas.95.7.3720
发表时间：
1998-03-31
影响因子：
11.1
作者：
Mrázek, J;Karlin, S
通讯作者：
Karlin, S
影响因子：
3.5
作者：
Salzberg, SL;Salzberg, AJ;Tomb, JF
通讯作者：
Tomb, JF