Brown J L, Wu C
Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Development. 1993 Jan;117(1):45-58. doi: 10.1242/dev.117.1.45.
The tramtrack (ttk) protein has been proposed as a maternally provided repressor of the fushi tarazu (ftz) gene in Drosophila embryos at the preblastoderm stage. Consistent with this hypothesis, we have detected by immunohistochemistry the presence of ttk protein in preblastoderm embryos. This is followed by a complete decay upon formation of the cellular blastoderm when ftz striped expression is at its peak. In addition, the highly complex pattern of zygotic ttk expression suggests specific functions for ttk late in development that are separate from the regulation of ftz. We have produced ttk protein ectopically in blastoderm-stage embryos transformed with a heat shock-ttk construct. Ectopic ttk caused complete or near-complete repression of the endogenous ftz gene, as well as significant repression of the pair-rule genes even skipped, odd skipped, hairy and runt. These findings suggest that specific repression by ttk (or by undiscovered repressors) may be more than an isolated phenomenon during the rapid cleavage divisions, a period when the need for genetic repression has not been generally anticipated.
轨道蛋白（tramtrack，ttk）被认为是母源性提供的一种阻遏物，在果蝇胚胎的胚盘形成前期抑制分节基因（fushi tarazu，ftz）。与这一假说相符的是，我们通过免疫组织化学检测到在胚盘形成前期胚胎中存在ttk蛋白。随后，当ftz条纹状表达达到峰值时，在细胞胚盘形成过程中该蛋白完全降解。此外，合子型ttk表达的高度复杂模式表明ttk在发育后期具有特定功能，这与对ftz的调控无关。我们利用热休克-ttk构建体在胚盘期胚胎中异位表达ttk蛋白。异位表达的ttk导致内源性ftz基因完全或近乎完全被抑制，同时配对规则基因even skipped、odd skipped、hairy和runt也受到显著抑制。这些发现表明，ttk（或未被发现的阻遏物）的特异性抑制可能并非快速卵裂期的孤立现象，而在此期间，基因抑制的需求通常未被普遍预期。
