八肋游仆虫大核基因组中组蛋白基因H4A和H4B的克隆及分析

Cloning and Analysis of H4A and H4B Genes from the Macronucleus of Euplotes octocarinatus

组蛋白作为核小体的基本组分,是染色质的结构和功能必需的。组蛋白的变体和修饰共同参与染色质修饰及基因的表达调控。真核生物细胞中的5种组蛋白在进化中高度保守,然而纤毛虫的组蛋白H4与其他真核生物相比有较大的差异。本实验应用PCR技术从八肋游仆虫(Euplotes octocarinatus)中获得了2种组蛋白H4基因,分别为H4A和H4B,GenBank登录号为:JN715068和JN715069。序列分析表明,H4A基因开放阅读框324 bp,预测编码107个氨基酸,分子量为11.6 ku,等电点为10.99。而H4B基因编码框384 bp,编码127个氨基酸,分子量为14.4 ku,等电点为9.93。Blast结果显示,H4A序列与其他生物中H4的一致性相对较高,达81%～94%,而H4B的一致性为36%～70%。H4A和H4B的一致性仅为44.7%。实时荧光定量PCR表明,H4A的转录本高于H4B。结果提示:在进化过程中八肋游仆虫可能进化出特殊的组蛋白H4基因,不同的组蛋白H4可能发挥不同的功能。

Histones are basic components of nueleosome and essential to chromatin structure and function. Histone posttranslational modifications and sequence variants jointly participate in modification of chromatin and regulation of gene expression. Histones are highly conserved proteins in different organisms. However, a high degree of variation was found in ciliate. In the study, H4A and H4B were cloned from Euplotes octocarinatus by PC R,GenBank accession number： JN715068 and JN715069. Sequences analysis showed that opening reading frame of the H4A gene was 324 bp, which encoded a 107 amino acid polypeptide with a predicted molecular mass of 11.6 ku and isoelectrie point of 10.99. The opening reading frame of the H4B gene was 384 bp, which encoded a 127 amino acid polypeptide with a predicted molecular mass of 14.4 ku and isoelectric point of 9.93. H4A gene shared a high identity of 81% -94% with reported H4 gene, while H4B shared an identity of 36% - 70% with H4 gene from other eukaryotes. H4A shared 44. 7% identity with H4B. Real-time PCR showed that H4A transcript was higher than that of H4B. The results indicate that the H4 gene has different variants in E. octocarinatus.