Zachar Z, Davison D, Garza D, Bingham P M
Genetics. 1985 Nov;111(3):495-515. doi: 10.1093/genetics/111.3.495.
The copia insertion responsible for the wa mutation is 3' to the white promotor and in the same transcriptional orientation as white. First, we have analyzed the effects of the wa copia insertion on levels of polyadenylated white transcripts and find large, developmentally programmed effects. Second, we have isolated and sequenced an LTR-excision event involving the copia insertion at wa. This represents the first documented case of an LTR-excision event in Drosophila. This single copia LTR has developmentally programmed effects on white transcript levels qualitatively similar to the intact copia element. Third, we have characterized the structures of white transcripts from wa. We find polyadenylated white transcripts apparently having 3' termini in or near the 3' LTR of the wa copia insertion, as has been reported in limited studies of wa transcription in adults by others. These earlier studies also revealed wa transcripts apparently corresponding to polyadenylated terminus formation in the 5' LTR of the copia transposon; however, our more detailed studies reveal that these transcripts probably have other origins and that little, if any, polyadenylated terminus formation for white transcripts occurs in the 5' LTR of the wa copia insertion. Moreover, we find no polyadenylated terminus formation for white transcripts occurring in the single LTR of the wa LTR-excision product. Fourth, we find that each of three mutant alleles at su(wa) produces elevated levels of several classes of RNAs apparently corresponding to transcriptional readthrough of the wa copia transposon. Elevated levels of one presumptive readthrough transcript were observed previously in one su(wa) mutant strain. Fifth, we have confirmed the existence of a transcript initiated in the 3' LTR of the wa copia insertion and find the levels of this transcript to be strongly influenced by developmental stage and genetic background. Lastly, we have analyzed white transcripts produced by the whd81b11 allele, which carries an insertion of copia in the opposite transcriptional orientation and in a different position than the wa copia insertion. In contrast to the wa copia insertion allele, the whd81b11 allele produces polyadenylated white transcript levels very similar to the w+ case at the stages examined. Moreover, the whd81b11 copia element apparently produced polyadenylated terminus formation in white transcripts and we observe no effect of the allelic state of su(wa) on apparent readthrough of this stop site.(ABSTRACT TRUNCATED AT 400 WORDS)
导致wa突变的copia插入位于白色基因启动子的3'端，且与白色基因处于相同的转录方向。首先，我们分析了wa copia插入对多聚腺苷酸化白色转录本水平的影响，发现了巨大的、受发育调控的效应。其次，我们分离并测序了一个涉及wa处copia插入的LTR切除事件。这是果蝇中首个有记录的LTR切除事件。这个单一的copia LTR对白色转录本水平具有受发育调控的效应，在性质上与完整的copia元件相似。第三，我们对来自wa的白色转录本结构进行了表征。我们发现多聚腺苷酸化的白色转录本的3'末端明显位于wa copia插入的3' LTR内或其附近，正如其他人对成年果蝇中wa转录的有限研究所报道的那样。这些早期研究还揭示了wa转录本明显对应于copia转座子5' LTR中的多聚腺苷酸化末端形成；然而，我们更详细的研究表明，这些转录本可能有其他来源，并且在wa copia插入的5' LTR中几乎没有白色转录本的多聚腺苷酸化末端形成（如果有的话）。此外，我们在wa LTR切除产物的单个LTR中未发现白色转录本的多聚腺苷酸化末端形成。第四，我们发现su(wa)的三个突变等位基因中的每一个都会使几类RNA的水平升高，这些RNA明显对应于wa copia转座子的转录通读。先前在一个su(wa)突变株中观察到一种推定的通读转录本水平升高。第五，我们证实了在wa copia插入的3' LTR中起始的转录本的存在，并发现该转录本的水平受到发育阶段和遗传背景的强烈影响。最后，我们分析了whd81b11等位基因产生的白色转录本，该等位基因携带一个与wa copia插入方向相反且位置不同的copia插入。与wa copia插入等位基因不同，在检查的阶段，whd81b11等位基因产生的多聚腺苷酸化白色转录本水平与w+情况非常相似。此外，whd81b11 copia元件显然在白色转录本中产生了多聚腺苷酸化末端形成，并且我们未观察到su(wa)的等位基因状态对该终止位点的明显通读有影响。（摘要截断于400字）
