Monesi N, Jacobs-Lorena M, Paçó-Larson M L
Departamento de Morfologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP 14049-900, Brasil.
Chromosoma. 1998 Dec;107(8):559-69. doi: 10.1007/s004120050342.
The BhC4-1 gene of the sciarid Bradysia hygida is located at DNA puff C4 and is amplified and actively transcribed in the salivary gland at the end of the last larval instar. We show here that a 3.6 kb fragment from the upstream region of the BhC4-1 gene is able to drive transcription in transgenic Drosophila specifically in prepupal salivary gland in a temporally regulated manner. The mRNA is present in maximal amounts in prepupae +3 h; in prepupae +9 h the levels of BhC4-1 mRNA decline, and it is no longer detected in pupae +24 h. Taken together these results suggest that most, if not all, of the key promoter regulatory elements were included in the DNA fragments employed to transform Drosophila. Moreover, strong expression of the transgenes implies conservation of the regulatory elements involved, since Drosophila transcription factors appear to recognize B. hygida regulatory DNA sequences. Quantitative Southern blot hybridization indicates that the sequences from DNA puff C4 are not amplified at detectable levels in salivary glands of transgenic prepupae when the BhC4-1 gene is transcribed. Transcription of a DNA puff in the absence of amplification indicates that the induction of these processes involves distinct mechanisms.
菌蚊（Bradysia hygida）的BhC4-1基因位于DNA泡C4处，在最后一龄幼虫末期的唾液腺中被扩增并活跃转录。我们在此表明，来自BhC4-1基因上游区域的一个3.6 kb片段能够驱动转基因果蝇中的转录，具体是在蛹前期唾液腺中以时间调控的方式进行。该mRNA在蛹前期+3小时时含量最高；在蛹前期+9小时时，BhC4-1 mRNA水平下降，在蛹期+24小时时不再检测到。综合这些结果表明，用于转化果蝇的DNA片段中包含了大部分（如果不是全部）关键启动子调控元件。此外，转基因的强表达意味着所涉及的调控元件具有保守性，因为果蝇转录因子似乎能够识别菌蚊的调控DNA序列。定量Southern印迹杂交表明，当BhC4-1基因转录时，转基因蛹前期唾液腺中DNA泡C4的序列未在可检测水平上被扩增。在没有扩增的情况下DNA泡的转录表明这些过程的诱导涉及不同的机制。
