Preservation of a pseudogene by gene conversion and diversifying selection
Preservation of a pseudogene by gene conversion and diversifying selection
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DOI：
10.1534/genetics.108.091918
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发表时间：
2008-09-01
期刊：
影响因子：
3.3
通讯作者：
Innan, Hideki
中科院分区：
文献类型：
--
作者：
Takuno, Shohei;Nishio, Takeshi;Innan, Hideki
位点间基因转换被认为是在重复基因中产生新的多态组合的关键机制。在主要组织亲和性复合体和自交不亲和基因中，重复基因之间的基因转换的重要性已经被认识到，这些基因可能受到多样化选择的影响。为了从理论上理解基因转换在这种情况下的潜在作用，我们在各种双基因座模型中进行了正向模拟。结果表明，在这两个基因座上进行多样化选择时，基因转化可以显著增加单倍型的数量。我们发现，基因转化的途径长度是决定基因转化效果的一个重要因素：在每个位点的基因转化率相同的情况下，较短的途径长度可以更有效地产生新的单倍型。当其中一个重复的基因被判定为假基因时，也会得到类似的结果。这表明，复制的基因，即使在沉默之后，也会通过基因转换增加另一个基因座的可变性。因此，在基因转化的存在下，重复基因的固定概率和寿命都会增加。在这些发现的基础上，我们提出了一种新的重复基因保存方案：当原始供体基因处于多样化选择时，即使在假基因之后，通过基因转换也可以保存重复副本。
Interlocus gene conversion is considered a crucial mechanism for generating novel combinations of polymorphisms in duplicated genes. The importance of gene conversion between duplicatd genes has been recognized in the major histocompatibility complex and self-incompatibility genes, which are likely subject to diversifying selection. To theoretically understand the potential role of gene conversion in such situations, forward simulations are performed in various two-locus models. The result shown that gene conversion could significantly increase the number of haplotypes when diversifying selection works on both loci. We find that the tract length of gene conversion is an important factor to determine the efficacy of gene conversion: shorter tract lengths can more effectively generate novel haplotypes given the gene conversioin rate per site is the same. Similar results are also obtained when one of the duplicated genes is asumed to be a pseudogene. It is suggested that a duplicated gene, even after being silenced, will congtribute to increasing the variability in the other locus through gene conversion. Consequently, the fixation probability and longevity of duplicated genes increase under the presence of gene conversion. On the basis of these findings, we propose a new scenario for the preservation of duplicated gene: when the original donor gene is under diversifying selection, a duplicated copy can be preserved by gene conversion even after it is pseudogenized.