The distribution of L1 and Alu retroelements in relation to GC content on human sex chromosomes is consistent with the ectopic recombination model
The distribution of L1 and Alu retroelements in relation to GC content on human sex chromosomes is consistent with the ectopic recombination model
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DOI：
10.1007/s00239-005-0275-0
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发表时间：
2006-10-01
影响因子：
3.9
通讯作者：
Krambeck, Hans-Juergen
中科院分区：
文献类型：
--
作者：
Abrusan, Gyorgy;Krambeck, Hans-Juergen
Alu和L1逆转录元件在人类基因组中的分布随年龄而变化。活性逆转录因子靶向AT丰富的区域，但它们在GC和基因丰富的基因组区域中的频率随着插入年龄的增加而增加。目前，对于产生这种模式的机制还没有达成共识。本文通过对性染色体上重复序列GC分布的详细分析，验证了对重复序列间异位重组引起的有害缺失的选择是L1 s和Alus分布不均匀的主要原因这一假设。结果表明：（1）与常染色体和X染色体不同，L1在Y染色体GC富集区不富集，而Alu在Y染色体GC富集区有少量富集;（2）在Y染色体上，Alu和L1密度呈正相关，而在其他染色体上呈负相关;（3）在4号染色体和X染色体的基因缺失区，Alus和L1 s的分布没有向GC富集区移动。此外，我们表明，虽然本地GC含量的长L1插入低于平均水平，他们的选择性损失重组染色体是不是富集的主要原因，古老的L1 s在GC丰富的地区。这些结果支持了异位重组导致Alu和L1分布向基因组的基因丰富区域转移的假设。
The distribution of Alu and L1 retroelements in the human genome changes with their age. Active retroelements target AT-rich regions, but their frequency increases in GC- and gene-rich regions of the genome with increasing age of the insertions. Currently there is no consensus on the mechanism generating this pattern. In this paper we test the hypothesis that selection against deleterious deletions caused by ectopic recombination between repeats is the main cause of the inhomogeneous distribution of L1s and Alus, by means of a detailed analysis of the GC distribution of the repeats on the sex chromosomes. We show that (1) unlike on the autosomes and X chromosome, L1s do not accumulate on the Y chromosome in GC-rich regions, whereas Alus accumulate there to a minor extent; (2) on the Y chromosome Alu and L1 densities are positively correlated, unlike the negative correlation on other chromosomes; and (3) in gene-poor regions of chromosome 4 and X, the distribution of Alus and L1s does not shift toward GC-rich regions. In addition, we show that although local GC content of long L1 insertions is lower than average, their selective loss from recombining chromosomes is not the main cause of the enrichment of ancient L1s in GC-rich regions. The results support the hypothesis that ectopic recombination causes the shift of Alu and L1 distributions toward the gene-rich regions of the genome.