Crowley T E, Meyerowitz E M
Dev Biol. 1984 Mar;102(1):110-21. doi: 10.1016/0012-1606(84)90179-9.
The 68C region of the Drosophila melanogaster salivary gland polytene chromosomes harbors the structural genes for the three salivary gland glue proteins sgs-3, sgs-7, and sgs-8. This region is puffed during the third larval instar, the stage when glue proteins are being produced in the salivary glands. The puff regresses near the end of the third instar as a result of an increased titer of the steroid hormone ecdysterone in the larval hemolymph. The experiments reported here were designed to determine whether the ecdysterone effect on puffing at 68C is correlated with hormone effects on expression of the three puff RNAs. In the first series of experiments, it is shown that there is a more rapid disappearance of 68C RNA transcripts from salivary glands cultured in the presence of ecdysterone than from glands cultured in its absence. The second set of experiments, in which 68C transcripts were pulse-labeled in salivary glands cultured in the presence or absence of hormone, demonstrates that one effect of ecdysterone is to cause a sharp reduction in the rate at which newly synthesized 68C transcripts accumulate. The final experiments follow the time required for ecdysterone to produce this effect, and show that it occurs in salivary glands exposed to the hormone for as little as 15 min. In all of the experiments, the RNA products of the Sgs-3, Sgs-7, and Sgs-8 genes acted coordinately.
黑腹果蝇唾液腺多线染色体的68C区域包含三种唾液腺胶蛋白sgs - 3、sgs - 7和sgs - 8的结构基因。该区域在幼虫第三龄期出现胀泡，此阶段唾液腺中正在产生胶蛋白。由于幼虫血淋巴中类固醇激素蜕皮甾酮的滴度增加，胀泡在第三龄期末期消退。本文报道的实验旨在确定蜕皮甾酮对68C处胀泡的影响是否与激素对三种胀泡RNA表达的影响相关。在第一系列实验中，结果表明，与在无蜕皮甾酮条件下培养的腺体相比，在有蜕皮甾酮存在的情况下培养的唾液腺中，68C RNA转录本的消失更快。第二组实验中，在有或无激素存在的情况下培养的唾液腺中对68C转录本进行脉冲标记，结果表明蜕皮甾酮的一个作用是导致新合成的68C转录本积累速率急剧降低。最后的实验追踪了蜕皮甾酮产生这种作用所需的时间，并表明在暴露于该激素仅15分钟的唾液腺中就会出现这种情况。在所有实验中，Sgs - 3、Sgs - 7和Sgs - 8基因的RNA产物协同作用。
