Joint Study on Nature of Histone Variants by Gene Disruption

44个鸡H1和核心组蛋白基因中有39个位于110 kb的主要组蛋白基因簇中。在这项研究中，使用基因打靶技术，我们产生了几个DT4O突变体，分别是缺乏一个或两个特定的组蛋白基因，一个等位基因的主基因簇的110 kb，一个约57 kb的片段的集群携带21个基因，和11的12个H1基因拷贝。对所产生的突变体的系统分析使我们得出一些值得注意的结论，如下：1）所有组蛋白基因家族都具有内在的能力，以补偿大约一半的自身组分的缺失，并基于剩余基因表达的增加来维持每个组蛋白亚型的量处于化学计量平衡，而不管主要基因簇的一个等位基因的完全破坏或两个等位基因的大约一半片段的破坏。因此，主要组蛋白基因簇的一个等位基因足以用于细胞增殖。2）12个H1基因拷贝中的11个的缺失不影响细胞功能，即生长速率和整体染色质结构。这些结果表明，只有一个拷贝的H1基因就足以用于细胞增殖。3）在缺失簇的一个等位基因的情况下，蛋白质模式没有改变，这是由于任何组蛋白变体的组成没有变化，但是在缺失簇的大约一半片段的情况下，蛋白质模式发生变化，并且后者加上更多的H1基因，由于H1和核心变体的质量变化。4）突变体中的蛋白质模式分别改变，缺乏特定的H1和H2B变体。的可变蛋白质是特定的相应的突变体，这表明H1和核心变种应单独参与特定基因的表达调控，通过改变定位在特定的基因组区域的chornatin结构。

Thirty-nine of the 44 chicken H1 and core histone genes are located in a major histone gene cluster of 110 kb. In this study, using gene targeting techniques, we generated several DT4O mutants, respectively, which are devoid of one or two particular histone genes, one allele of the major gene cluster of 110 kb, an approximately 57 kb segment of the cluster carrying 21 genes, and 11 of the 12 H1 gene copies. Systematic analyses of the resultant mutants led us to some noticeable conclusions, as follows.1)All of the histone gene families have the inherent ability to compensate for the deletion of approximately half of their own constituents, and to maintain the amount of each of the histone subtypes in stoichiometric balance, based on increases in the expression of the remaining genes, regardless of the complete disruption of one allele of the major gene cluster or the disruption of approximately half segments of the two alleles. Therefore, one allele of the major histone gene cluster is enough for cell proliferation.2)The deletion of 11 of the 12 H1 gene copies does not affect cell functions, i.e. the growth rate and global chromatin structure. These results indicate that only one copy of the H1 genes is enough for cell proliferation.3)The protein patterns are not altered in the case of the deletion of one allele of the cluster, due to no changes in the composition of any histone variant, but vary in the case of the deletion of approximately half segments of the cluster, and the latter plus more Hl gene(s), due to changes in the quality of the H1 and core variants.4)The protein patterns are altered in the mutants, respectively, lacking particular Hl and H2B variants. The variable proteins are specific for the corresponding mutants, suggesting that the H1 and core variants should be individually involved in regulation of the expression of specific genes, through alterations in the chrornatin structure localized in specific genomic regions.