SILENCERS IN ABDOMINAL-B, A HOMEOTIC DROSOPHILA GENE
SILENCERS IN ABDOMINAL-B, A HOMEOTIC DROSOPHILA GENE
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DOI：
10.1002/j.1460-2075.1993.tb05785.x
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发表时间：
1993-04-01
期刊：
影响因子：
11.4
通讯作者：
BIENZ, M
中科院分区：
文献类型：
--
作者：
BUSTURIA, A;BIENZ, M
同源基因决定细胞的发育命运。限制它们沿身体轴的表达对于正常发育至关重要。我们通过测试基因组 Abd-B 片段在转化胚胎中赋予 β-半乳糖苷酶（β-gal）表达的能力，在果蝇同源异型基因 Abdominal-B (Abd-B) 中寻找顺式调控序列。其中一个 Abd-B 片段称为 IAB5，介导沿体轴限制到 Abd-B 表达域的 β-gal 模式。间隙突变体中 IAB5 模式的改变提供了间隙基因 hurchback、Kruppel 和 knirps 的蛋白质产物通过 IAB5 作为阻遏物的证据。前部 Abd-B 表达限制显然是由 Kruppel 抑制决定的，而 knirps 抑制子可能是 Abd-B 域内分级 Abd-B 表达的原因。 IAB5 和另外两个称为 MCP 和 FAB 的片段显示出区域特异性沉默活性：它们远距离抑制由相连的异源增强子介导的 β-gal 表达。沉默需要 hurchback 以及 Polycomb 功能，并且显然可以在整个胚胎发生过程中维持 Abd-B 表达限制。我们得出结论，转录抑制是在多个层面上控制 Abd-B 表达的关键机制。 Abd-B 和另一种同源异型果蝇基因 Ultrabithorax 的控制之间的惊人相似之处可能表明同源异型基因调控的普遍原理。
Homeotic genes determine the developmental fates of cells. Restriction of their expression along the body axis is of prime importance for normal development. We searched for cis-regulatory sequences within Abdominal-B (Abd-B), a homeotic Drosophila gene, by testing genomic Abd-B fragments for their ability to confer beta-galactosidase beta-gal) expression in transformed embryos. One of the Abd-B fragments, called IAB5, mediates a beta-gal pattern restricted along the body axis to the Abd-B expression domain. Alterations of the IAB5 pattern in gap mutants provide evidence that the protein products of the gap genes hunchback, Kruppel and knirps act as repressors through IAB5. The anterior Abd-B expression limit is apparently determined by Kruppel repression, whereas the knirps repressor may be responsible for the graded Abd-B expression within the Abd-B domain. IAB5 and two other fragments called MCP and FAB show region-specific silencing activity: they suppress at a distance beta-gal expression mediated by a linked heterologous enhancer. Silencing requires hunchback as well as Polycomb function and evidently provides maintenance of Abd-B expression limits throughout embryogenesis. We conclude that transcriptional repression is a key mechanism operating at multiple levels to control Abd-B expression. The striking similarities between the control of Abd-B and of Ultrabithorax, another homeotic Drosophila gene, may point to a universal principle underlying homeotic gene regulation.