Histone Gene Multiplicity and Position Effect Variegation in DROSOPHILA MELANOGASTER.
Histone Gene Multiplicity and Position Effect Variegation in DROSOPHILA MELANOGASTER.
复制标题
果蝇组蛋白基因多样性和位置效应变异。
作者：
G. D. Moore;D. Sinclair;T. Grigliatti
野生型果蝇的组蛋白基因每个单倍体基因组重复 100-150 次，位于 2 号染色体对应多线带 39D2-3 至 E1-2 的区段中。通过测量与 39D-E 片段缺失的基因型中位置效应变异相关的基因失活修饰，分析了组蛋白基因多样性改变对染色质结构的影响。在因去除组蛋白基因复合体的缺陷而杂合的基因型中，杂色基因活跃的细胞比例增加。删除与组蛋白基因复合体相邻的片段的删除对杂色基因的表达没有影响。与组蛋白基因多样性减少相关的位置效应杂色的抑制适用于 X 连锁基因和常染色体杂色基因。常染色体和性染色体异染色质所产生的位置效应可以通过删除组蛋白基因复合物来抑制。这种抑制与 Y 染色体的存在无关。仅删除组蛋白基因复合物远端部分的缺陷也具有抑制位置效应杂色的能力。组蛋白基因复合物的重复不会增强位置效应杂色。母体基因组中组蛋白基因复合物的缺失或重复对组蛋白基因多样性正常的后代的杂色程度没有影响。这些结果是根据组蛋白基因复合物的组织及其表达控制的当前知识进行讨论的。
The histone genes of wild-type Drosophila melanogaster are reiterated 100-150 times per haploid genome and are located in the segment of chromosome 2 that corresponds to polytene bands 39D2-3 to E1-2. The influence of altered histone gene multiplicity on chromatin structure has been assayed by measuring modification of the gene inactivation associated with position effect variegation in genotypes bearing deletions of the 39D-E segment. The proportion of cells in which a variegating gene is active is increased in genotypes that are heterozygous for a deficiency that removes the histone gene complex. Deletions that remove segments adjacent to the histone gene complex have no effect on the expression of variegating genes. Suppression of position effect variegation associated with reduction of histone gene multiplicity applies to both X-linked and autosomal variegating genes. Position effects exerted by both autosomal and sex-chromosome heterochromatin were suppressible by deletions of the histone gene complex. The suppression was independent of the presence of the Y chromosome. A deficiency that deletes only the distal portion of the histone gene complex also has the ability to suppress position effect variegation. Duplication of the histone gene complex did not enhance position effect variegation. Deletion or duplication of the histone gene complex in the maternal genome had no effect on the extent of variegation in progeny whose histone gene multiplicity was normal. These results are discussed with respect to current knowledge of the organization of the histone gene complex and control of its expression.