Andrew D J, Horner M A, Petitt M G, Smolik S M, Scott M P
Department of Developmental Biology, Stanford University School of Medicine, CA 94305-5427.
EMBO J. 1994 Mar 1;13(5):1132-44. doi: 10.1002/j.1460-2075.1994.tb06362.x.
Each of the homeotic genes of the HOM or HOX complexes is expressed in a limited domain along the anterior-posterior axis. Each homeotic protein directs the formation of characteristic structures, such as wings or ribs. In flies, when a heat shock-inducible homeotic gene is used to produce a homeotic protein in all cells of the embryo, only some cells respond by altering their fates. We have identified genes that limit where the homeotic gene Sex combs reduced (Scr) can affect cell fates in the Drosophila embryo. In the abdominal cuticle Scr is prevented from inducing prothoracic structures by the three bithorax complex (BX-C) homeotic genes. However, two of the BX-C homeotic genes, Ultrabithorax (Ubx) and abdominal-A (abd-A), have no effect on the ability of Scr to direct the formation of salivary glands. Instead, salivary gland induction by Scr is limited in the trunk by the homeotic gene teashirt (tsh) and in the last abdominal segment by the third BX-C gene, Abdominal-B (AbdB). Therefore, spatial restrictions on homeotic gene activity differ between tissues and result both from the regulation of homeotic gene transcription and from restraints on where homeotic proteins can function.
HOM或HOX复合体中的每个同源异型基因都沿前后轴在有限的区域表达。每个同源异型蛋白指导特征性结构的形成，如翅膀或肋骨。在果蝇中，当使用热休克诱导型同源异型基因在胚胎的所有细胞中产生同源异型蛋白时，只有一些细胞通过改变命运做出反应。我们已经鉴定出了一些基因，它们限制了同源异型基因性梳减少（Scr）在果蝇胚胎中影响细胞命运的位置。在腹部表皮中，Scr被三个双胸复合体（BX-C）同源异型基因阻止诱导前胸结构。然而，BX-C的两个同源异型基因，超双胸（Ubx）和腹部A（abd-A），对Scr指导唾液腺形成的能力没有影响。相反，Scr对唾液腺的诱导在躯干中受同源异型基因T恤衫（tsh）限制，在最后一个腹部节段受第三个BX-C基因腹部B（AbdB）限制。因此，同源异型基因活性的空间限制在不同组织之间存在差异，这既源于同源异型基因转录的调控，也源于对同源异型蛋白发挥功能位置的限制。
