Dozier C, Kagoshima H, Niklaus G, Cassata G, Bürglin T R
Division of Cell Biology, Biozentrum, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
Dev Biol. 2001 Aug 15;236(2):289-303. doi: 10.1006/dbio.2001.0325.
Caenorhabditis elegans has four members of the Six/sine oculis class of homeobox genes, ceh-32, ceh-33, ceh-34, and ceh-35. Proteins encoded by this gene family are transcription factors sharing two conserved domains, the homeodomain and the Six/sine oculis domain, both involved in DNA binding. ceh-32 expression was detected during embryogenesis in hypodermal and neuronal precursor cells and later in descendants of these cells as well as in gonadal sheath cells. RNAi inactivation studies suggest that ceh-32 plays a role in head morphogenesis, like vab-3, the C. elegans Pax-6 orthologue. ceh-32 and vab-3 are coexpressed in head hypodermal cells and ceh-32 mRNA levels are reduced in vab-3 mutants. Moreover, ectopic expression of VAB-3 in transgenic worms is able to induce ceh-32 ectopically. In addition, we demonstrate that VAB-3 is able to bind directly to the ceh-32 upstream regulatory region in vitro and to activate reporter gene transcription in a yeast one-hybrid system. Our results suggest that VAB-3 acts upstream of ceh-32 during head morphogenesis and directly induces ceh-32. Thus, ceh-32 appears to be the first target gene of VAB-3 identified so far.
秀丽隐杆线虫有四个同源异型盒基因Six/sine oculis家族成员，即ceh-32、ceh-33、ceh-34和ceh-35。该基因家族编码的蛋白质是转录因子，共享两个保守结构域，即同源结构域和Six/sine oculis结构域，二者均参与DNA结合。在胚胎发育期间，在皮下和神经前体细胞中检测到ceh-32的表达，随后在这些细胞的后代以及性腺鞘细胞中也检测到其表达。RNA干扰失活研究表明，ceh-32在头部形态发生中发挥作用，就像秀丽隐杆线虫Pax-6直系同源基因vab-3一样。ceh-32和vab-3在头部皮下细胞中共表达，并且在vab-3突变体中ceh-32的mRNA水平降低。此外，VAB-3在转基因蠕虫中的异位表达能够异位诱导ceh-32。另外，我们证明VAB-3能够在体外直接结合ceh-32上游调控区，并在酵母单杂交系统中激活报告基因转录。我们的结果表明，在头部形态发生过程中VAB-3在ceh-32的上游起作用，并直接诱导ceh-32。因此，ceh-32似乎是迄今为止鉴定出的VAB-3的首个靶基因。
