Merli C, Bergstrom D E, Cygan J A, Blackman R K
Department of Cell and Structural Biology, University of Illinois, Urbana 61801, USA.
Genes Dev. 1996 May 15;10(10):1260-70. doi: 10.1101/gad.10.10.1260.
Although enhancers can exert their influence over great distances, their effect is generally limited to a single gene. To discern the mechanism by which this constraint can he mediated, we have studied three neighboring Drosophila genes: decapentaplegic (dpp), SLY1 homologous (Slh) and out at first (oaf). Several dpp enhancers are positioned close to Slh and oaf, and yet these genes are unaffected by the dpp elements. However, when a transposon is located within the oaf gene, the dpp enhancers activate the more distant transposon promoters while still ignoring the closer Slh and oaf start sites. To test whether this promoter specificity accounts for the regulatory autonomy normally found for the three genes, we used in vivo gene targeting to replace the oaf promoter with a dpp-compatible one in an otherwise normal chromosome. Strikingly, this chimeric gene is now activated by the dpp enhancers. Thus, the properties of the promoters themselves are sufficient to mediate the autonomous regulation of genes in this region.
尽管增强子可以在远距离发挥作用，但其作用通常仅限于单个基因。为了弄清楚这种限制是如何介导的，我们研究了果蝇的三个相邻基因：十全大补基因（dpp）、SLY1同源基因（Slh）和初出茅庐基因（oaf）。几个dpp增强子位于靠近Slh和oaf的位置，但这些基因不受dpp元件的影响。然而，当一个转座子位于oaf基因内时，dpp增强子会激活距离更远的转座子启动子，而仍然忽略更近的Slh和oaf起始位点。为了测试这种启动子特异性是否解释了这三个基因通常具有的调控自主性，我们在体内进行基因靶向，用一个与dpp兼容的启动子替换正常染色体上的oaf启动子。令人惊讶的是，这个嵌合基因现在被dpp增强子激活了。因此，启动子自身的特性足以介导该区域基因的自主调控。
