Dosage-dependent modifiers of position effect variegation in Drosophila and a mass action model that explains their effect.
Dosage-dependent modifiers of position effect variegation in Drosophila and a mass action model that explains their effect.
复制标题
果蝇中位置效应杂色的剂量依赖性修饰剂以及解释其效应的质量作用模型。
DOI：
10.1093/genetics/120.1.181
复制
发表时间：
1988
期刊：
影响因子：
3.3
通讯作者：
Tartof,KD
中科院分区：
文献类型：
--
作者：
Locke,J;Kotarski,MA;Tartof,KD
用p元素诱变方法诱导了12个位置效应变异显性增强子，分别代表黑腹果蝇第2和第3染色体上的4个位点。这些突变中有7个是细胞学上可见的重复，3个是缺陷，而不是简单的转座子插入。重复定义了两个不同的区域，每个区域都与一个基因座相吻合，该基因座也表现为显性单倍依赖的杂色抑制因子。相反，其中两个缺陷与一个包含单倍依赖性杂色增强子的区域重叠，而该区域的重复作用抑制杂色。第三个缺陷定义了另一个单倍依赖的增强子。这些数据表明，能够通过改变野生型基因拷贝数以对跖方式改变变异的基因座可以分为两个相互作用的类。I类修饰剂在重复时增强杂色或在缺乏时抑制杂色。II类修饰符在缺乏时增强，而在复制时抑制。根据我们和其他人的数据，我们提出在果蝇中大约有20到30个修饰变异的显性位点。大多数修饰语似乎属于I类，而迄今为止只确定了两个II类修饰语。根据这些观察结果，我们提出了一个基于质量作用定律的模型，以了解这些抑制-增强基因座的功能。我们提出，每一类修饰子编码异染色质的一个结构蛋白成分，它们对变异的影响是它们在位置效应的染色体位点上对异染色质组装程度的剂量依赖性影响的结果。进一步提出，II类修饰剂可能直接抑制I类产物，结合到定义异染色质边界的假设终止位点或促进常染色质形成。与我们的质量作用模型一致，我们发现两种增强剂组合在一起产生加性效应而不是上位性效应。此外，由于不同的增强子在不同的变异突变体上具有不同的相对强度，我们认为异色结构域是由蛋白质的组合结合构建的。这里提出的质量作用模型对任何组装驱动的反应都具有普遍意义，并对理解各种生物现象具有重要意义。（摘要删节为400字）
Twelve dominant enhancers of position effect variegation, representing four loci on the second and third chromosomes of Drosophila melanogaster, have been induced by P-element mutagenesis. Instead of simple transposon insertions, seven of these mutations are cytologically visible duplications and three are deficiencies. The duplications define two distinct regions, each coinciding with a locus that also behaves as a dominant haplo-dependent suppressor of variegation. Conversely, two of the deficiencies overlap with a region that contains a haplo-dependent enhancer of variegation while duplications of this same region act to suppress variegation. The third deficiency defines another haplo-dependent enhancer. These data indicate that loci capable of modifying variegation do so in an antipodal fashion through changes in the wild-type gene copy number and may be divided into two reciprocally acting classes. Class I modifiers enhance variegation when duplicated or suppress variegation when deficient. Class II modifiers enhance when deficient but suppress when duplicated. From our data, and those of others, we propose that in Drosophila there are about 20 to 30 dominant loci that modify variegation. Most appear to be of the class I type whereas only two class II modifiers have been identified so far. From these observations we put forth a model, based on the law of mass action, for understanding how such suppressor-enhancer loci function. We propose that each class I modifier codes for a structural protein component of heterochromatin and their effects on variegation are a consequence of their dosage dependent influence on the extent of the assembly of heterochromatin at the chromosomal site of the position effect. It is further proposed that class II modifiers may inhibit the class I products directly, bind to hypothetical termination sites that define heterochromatin boundaries or promote euchromatin formation. Consistent with our mass action model we find that combining two enhancers together produce additive and not epistatic effects. Also, since different enhancers have different relative strengths on different variegating mutants, we suggest that heterochromatic domains are constructed by a combinatorial association of proteins. The mass action model proposed here is of general significance for any assembly driven reaction and has implications for understanding a wide variety of biological phenomena.(ABSTRACT TRUNCATED AT 400 WORDS)
登录
查看更多内容
影响因子：
3.3
作者：
B. Ephrussi;J. L. Herold
通讯作者：
J. L. Herold
果蝇α-甘油磷酸脱氢酶的电泳变体
影响因子：
56.9
作者：
E. Grell
通讯作者：
E. Grell
黑腹果蝇从粗糙型向野生型的逆转。
影响因子：
3.3
作者：
B. Kaufmann
通讯作者：
B. Kaufmann
含有乙醇脱氢酶结构基因的果蝇常染色体小区域的遗传学。
影响因子：
3.3
作者：
M. Ashburner
通讯作者：
M. Ashburner
影响因子：
64.5
作者：
K. Tartof;C. Hobbs;Marilyn Jones
通讯作者：
K. Tartof;C. Hobbs;Marilyn Jones