Erhart M A, Simons K S, Weaver S
Department of Biological Sciences, University of Illinois, Chicago 60680.
Mol Biol Evol. 1985 Jul;2(4):304-20. doi: 10.1093/oxfordjournals.molbev.a040353.
We have determined the complete nucleotide sequence of the two nonallelic adult beta-globin genes of the C57BL/10 mouse. These genes, designated beta s and beta t, show a sequence similarity of 99.6% over the region bordered by the translational start and stop codons. Both beta s and beta t encode functional polypeptide chains that are identical. A comparison of the C57BL/10 beta-globin haplotype, Hbbs, with that of the BALB/c mouse, Hbbd, suggests that the two haplotypes have distinct evolutionary histories. The two adult beta-globin genes of the Hbbd haplotype, beta dmaj and beta dmin, are 16% divergent at the nucleotide level and encode distinct polypeptides that are synthesized in differing amounts. Our analysis indicates that a gene correction mechanism has been operating on the Hbbs chromosome to keep beta s and beta t evolving in concert, whereas on the Hbbd chromosome, beta dmin has diverged considerably from beta dmaj. We suggest that gene conversion is responsible for the maintained similarity of the Hbbs genes. Furthermore, we attribute the divergence of the Hbbd genes in part to the absence of a region of simple-sequence DNA within the large intervening sequence of beta dmin. We propose that this region of DNA plays a role in facilitating gene conversion. The deletion of this area in beta dmin introduced a block of nonhomology between the beta dmaj-beta dmin gene pair and thus may have inhibited further gene correction within the Hbbd haplotype.
我们已经确定了C57BL/10小鼠的两个非等位成年β-珠蛋白基因的完整核苷酸序列。这些基因，命名为βs和βt，在由翻译起始和终止密码子界定的区域内显示出99.6%的序列相似性。βs和βt都编码相同的功能性多肽链。将C57BL/10β-珠蛋白单倍型Hbbs与BALB/c小鼠的Hbbd单倍型进行比较，表明这两种单倍型具有不同的进化历史。Hbbd单倍型的两个成年β-珠蛋白基因βdmaj和βdmin在核苷酸水平上有16%的差异，编码不同的多肽，且合成量不同。我们的分析表明，一种基因校正机制一直在Hbbs染色体上起作用，以使βs和βt协同进化，而在Hbbd染色体上，βdmin已与βdmaj有很大程度的分化。我们认为基因转换是Hbbs基因保持相似性的原因。此外，我们将Hbbd基因的分化部分归因于βdmin的大间隔序列中不存在简单序列DNA区域。我们提出，这个DNA区域在促进基因转换中起作用。βdmin中该区域的缺失在βdmaj-βdmin基因对之间引入了一段非同源性，因此可能抑制了Hbbd单倍型内的进一步基因校正。
