Ohshiro Tomokazu, Emori Yasufumi, Saigo Kaoru
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo 113-0033, Japan.
Mech Dev. 2002 Jun;114(1-2):3-11. doi: 10.1016/s0925-4773(02)00042-4.
Spatially and temporally regulated activity of Branchless/Breathless signaling is essential for trachea development in Drosophila. Early ubiquitous breathless (btl) expression is controlled by binding of Trachealess/Tango heterodimers to the btl minimum enhancer. Branchless/Breathless signaling includes a Sprouty-dependent negative feedback loop. We show that late btl expression is a target of Branchless/Breathless signaling and hence, Branchless/Breathless signaling contains a positive feedback loop, which may guarantee a continuous supply of fresh receptors to membranes of growing tracheal branch cells. Branchless/Breathless signaling activates MAP-kinase, which in turn, activates late btl expression and destabilizes Anterior-open, a repressor for late btl expression. Biochemical and genetic analysis indicated that the minimum btl enhancer includes binding sites of Anterior-open.
无分支/无呼吸信号在空间和时间上的调控活性对于果蝇气管发育至关重要。早期广泛存在的无呼吸（btl）表达是由无气管/探戈异二聚体与btl最小增强子的结合所控制的。无分支/无呼吸信号包括一个依赖于Sprouty的负反馈环。我们发现晚期btl表达是无分支/无呼吸信号的一个靶点，因此，无分支/无呼吸信号包含一个正反馈环，这可能保证向正在生长的气管分支细胞的膜持续供应新鲜的受体。无分支/无呼吸信号激活丝裂原活化蛋白激酶（MAP激酶），而MAP激酶反过来又激活晚期btl表达，并使前开放蛋白（一种晚期btl表达的抑制因子）不稳定。生化和遗传学分析表明，btl最小增强子包含前开放蛋白的结合位点。
