A NEW HOMEOTIC MUTATION IN THE DROSOPHILA BITHORAX COMPLEX REMOVES A BOUNDARY SEPARATING 2 DOMAINS OF REGULATION
A NEW HOMEOTIC MUTATION IN THE DROSOPHILA BITHORAX COMPLEX REMOVES A BOUNDARY SEPARATING 2 DOMAINS OF REGULATION
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DOI：
10.1002/j.1460-2075.1990.tb07439.x
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发表时间：
1990-08-01
期刊：
影响因子：
11.4
通讯作者：
KARCH, F
中科院分区：
文献类型：
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作者：
GYURKOVICS, H;GAUSZ, J;KARCH, F
双胸复合体确定了果蝇的5-14副片段的身份。虽然已经鉴定出9个片段特异性功能，abx/bx， bxd/pbx和iab-2至iab-8,9，但整个双胸复合体似乎只编码Ubx， abd-A和Abd-B三类蛋白质。许多观察结果表明，这些副片段特异性功能是Ubx、abd-A和Abd-B的正向顺式调控元件。我们报道了一个新的功能获得突变Fab-7的分子遗传学，它将第11段转化为第12段。顺式诱导的Abd-B突变（其中一个去除了Abd-B同源盒）导致显性表型的逆转，表明Fab-7错误调节了Abd-B。Abd-B转录单元下游30kb处的一个4kb缺失是Fab-7表型的唯一原因。我们认为，片段特异性功能存在于沿染色体顺序和独立“打开”的DNA结构域中。一旦一个结构域被打开，其中的顺式调控序列就可以发挥它们的功能。我们提出，Fab-7的缺失消除了分隔ab-6和ab-7顺式调控区域的边界（para -片段11和12特有的功能），允许ab-6的开放配置侵入para - 11中的ab-7。我们的发现有力地支持了这一点，即不仅在iab-7中，而且在iab-6中，Fab-7可以被病变引起恢复。
The bithorax complex specifies the identity of parasegments 5-14 of Drosophila. Although nine parasegment-specific functions, abx/bx, bxd/pbx and iab-2 to iab-8,9 have been identified, the whole bithorax complex appears to encode only three classes of proteins, Ubx, abd-A and Abd-B. Many observations suggest that the parasegment-specific functions act as positive cis-regulatory elements of Ubx, abd-A and Abd-B. We report the molecular genetics of a new gain-of-function mutation, Fab-7, which transforms parasegment 11 into parasegment 12. Induction of Abd-B mutations in cis (one of which removes the Abd-B homeobox) causes reversion of the dominant phenotype, demonstrating that Fab-7 misregulates Abd-B. A 4 kb deletion, 30 kb downstream from the Abd-B transcription unit, is solely responsible for the Fab-7 phenotype. We consider that the parasegment-specific functions lie in DNA domains that are sequentially and independently ''opened'' along the chromosome. Once a domain is opened, the cis-regulatory sequences within it can carry out their function. We propose that the Fab-7 deletion removes a boundary separating the iab-6 and iab-7 cis-regulatory regions (the functions specific for parasegments 11 and 12) allowing the open configuration of iab-6 to invade iab-7 in parasegment 11. This is strongly supported by our finding that Fab-7 can be caused to revert by lesions not only in iab-7 but also in iab-6.