A switch in Broad-Complex zinc-finger isoform expression is regulated posttranscriptionally during the metamorphosis of Drosophila imaginal discs
A switch in Broad-Complex zinc-finger isoform expression is regulated posttranscriptionally during the metamorphosis of Drosophila imaginal discs
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DOI：
10.1006/dbio.1996.0140
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发表时间：
1996-07-10
影响因子：
2.7
通讯作者：
Fristrom, JW
中科院分区：
文献类型：
--
作者：
Bayer, CA;Holley, B;Fristrom, JW
宽复合物（BR-C）是20-羟基蜕皮激素调节层次的关键成员，协调果蝇变态过程中基因表达的变化。由BR-C编码的转录因子家族共有一个共同的氨基末端结构域，该结构域通过选择性剪接与四对C2 H2锌指结构域（Z1、Z2、Z3和Z4）之一融合。在这项研究中，我们研究的时间表达的转录编码每个BR-C锌指亚型-包括新发现的第四锌指结构域-在变态的成虫盘形成的表皮结构的成人头部和胸部。我们发现，所有BR-C锌指RNA亚型诱导作为一个主要的响应20-羟基蜕皮激素。然而，诱导BR-C RNA亚型表现出两个不同的表达谱。Z2、Z3和Z4 RNA亚型在蜕皮激素反应开始时积累到高水平，并在几小时后突然消失。相反，Z1 RNA亚型继续积累，而其他亚型下降，导致相对亚型水平的转换。使用特定于BR-C不同区域的探针，我们发现BR-C RNA亚型表达的开关似乎是转录后调节的，推测是由蜕皮激素反应因子引起的。我们建议，这种开关的结果从剪接受体位点选择的变化。最后，我们提出了一个模型，描述了这种时间开关亚型表达可以介导的BR-C功能的变化，从转录激活抑制，反之亦然，这是至关重要的协调下游靶基因的表达。(C)出版社：Academic Press，Inc.
The Broad-Complex (BR-C) is a key member of the 20-hydroxyecdysone regulatory hierarchy that coordinates changes in gene expression during Drosophila metamorphosis. The family of transcription factors encoded by the BR-C share a common amino-terminal domain which is fused by alternative splicing to one of four pairs of C2H2 zinc-finger domains (Z1, Z2, Z3, and Z4). In this study, we examine the temporal expression of transcripts encoding each BR-C zinc-finger isoform--including the newly discovered fourth zinc-finger domain--during the metamorphosis of imaginal discs which form the integumental structures of the adult head and thorax. We find that all BR-C zinc-finger RNA isoforms are induced as a primary response to 20-hydroxyecdysone. However, induced BR-C RNA isoforms exhibit two divergent expression profiles. The Z2, Z3, and Z4 RNA isoforms accumulate to high levels at the beginning of the ecdysone response and abruptly disappear after several hours. In contrast, the Z1 RNA isoform continues to accumulate while the others decline, resulting in a switch in relative isoform levels. Using probes specific to different regions of the BR-C, we show that the switch in BR-C RNA isoform expression appears to be posttranscriptionally regulated, presumably by ecdysone-responsive factors. We propose that this switch results from a change in splice acceptor site choice. Finally, we present a model describing how this temporal switch in isoform expression could mediate changes in BR-C function, from transcriptional activation to repression and vice versa, that are critical for coordinate downstream target gene expression. (C) 1996 Academic Press, Inc.