Breen T R, Chinwalla V, Harte P J
Department of Genetics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4955, USA.
Mech Dev. 1995 Jul;52(1):89-98. doi: 10.1016/0925-4773(95)00393-f.
We show that maintenance but not initiation of engrailed (en) gene expression in the Drosophila embryo requires trithorax (trx), which is also required to maintain stable long-term expression of the homeotic genes throughout the development. Like the homeotic genes, en expression is dependent on trx in only a subset of embryonic cells normally expressing en, including specific cells in the nervous system and the dorsal fat body cells surrounding the gonad. Loss of en expression in the dorsal fat body is correlated with the sterility of en females which also carry trx mutations. In addition, trx is required for normal en expression in the posterior compartment of the developing wing, reflected in enhancement of en phenotypes in en adults which also carry trx mutations. trx appears to be dispensable for maintenance of en expression in other embryonic cells. The trx protein binds to the region of the polytene chromosomes which contains the en gene, suggesting that trx regulates en expression directly by binding to the en regulatory region.
我们发现，果蝇胚胎中engrailed（en）基因表达的维持而非起始需要三体胸节（trx），trx在整个发育过程中对于维持同源异型基因的稳定长期表达也是必需的。与同源异型基因一样，en的表达仅在正常表达en的一部分胚胎细胞中依赖于trx，包括神经系统中的特定细胞以及性腺周围的背侧脂肪体细胞。背侧脂肪体中en表达的缺失与携带trx突变的en雌性果蝇的不育相关。此外，trx对于发育中翅膀后区正常的en表达是必需的，这体现在携带trx突变的en成年果蝇中en表型的增强。trx对于其他胚胎细胞中en表达的维持似乎是可有可无的。trx蛋白与包含en基因的多线染色体区域结合，这表明trx通过与en调控区域结合直接调节en的表达。
