Kojima Tetsuya, Tsuji Takuya, Saigo Kaoru
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Dev Biol. 2005 Mar 15;279(2):434-45. doi: 10.1016/j.ydbio.2004.12.005.
The subdivision of the developing field by region-specific expression of genes encoding transcription factors is an essential step during appendage development in arthropod and vertebrates. In Drosophila leg development, the distal-most region (pretarsus) is specified by the expression of homeobox genes, aristaless and Lim1, and its immediate neighbor (distal tarsus) is specified by the expression of a pair of Bar homeobox genes. Here, we show that one additional gene, clawless, which is a homolog of vertebrate Hox11/tlx homeobox gene family and formerly known as C15, is specifically expressed in the pretarsus and cooperatively acts with aristaless to repress Bar and possibly to activate Lim1. Similar to aristaless, the maximal expression of clawless requires Lim1 and its co-factor, Chip. Bar attenuates aristaless and clawless expression through Lim1 repression. Aristaless and Clawless proteins form a complex capable of binding to specific DNA targets, which cannot be well recognized solely by Aristaless or Clawless.
通过编码转录因子的基因的区域特异性表达对发育中的区域进行细分，是节肢动物和脊椎动物附肢发育过程中的一个重要步骤。在果蝇腿部发育过程中，最远端区域（跗节末端）由同源异型盒基因无触角基因（aristaless）和Lim1的表达所确定，而其紧邻区域（远端跗节）则由一对Bar同源异型盒基因的表达所确定。在这里，我们表明，另一个基因——无爪基因（clawless），它是脊椎动物Hox11/tlx同源异型盒基因家族的同源物，以前称为C15，在跗节末端特异性表达，并与无触角基因协同作用，抑制Bar基因，可能还激活Lim1基因。与无触角基因类似，无爪基因的最大表达需要Lim1及其辅因子Chip。Bar基因通过抑制Lim1来减弱无触角基因和无爪基因的表达。无触角蛋白和无爪蛋白形成一种能够结合特定DNA靶点的复合物，这种复合物不能仅由无触角蛋白或无爪蛋白很好地识别。
