Spencer C A, Gietz R D, Hodgetts R B
Nature. 1986;322(6076):279-81. doi: 10.1038/322279a0.
The many examples of overlap in the genes of various viruses and bacteria illustrate that the parsimonious utilization of the coding capacity of DNA is relatively common amongst prokaryotes. The recent discovery of a pupal cuticle gene within an intron of the completely unrelated Gart locus in Drosophila shows that overlapping transcription units also exist in higher organisms. However, the prevalence of such phenomena in unknown. We report here a quite different situation of overlap between the 3' termini of a pair of convergent transcription units in another region of the Drosophila genome. This 88-base-pair (bp) genomic region encodes the 3' terminus of the messenger RNA for the enzyme dopa decarboxylase (Ddc) and, in opposite orientation, the 3' terminus of the adjacent gene whose function is unknown. An analysis of the temporal and spatial distribution of the two transcripts within the organism shows that high levels of both transcripts are never concordant. However, within the testes, where the 3' transcript is maximally expressed, low levels of Ddc transcript were detected. This result raises the possibility that a hybrid molecule involving the two transcripts forms in vivo or that transcription interference occurs, with concomitant regulatory implications.
各种病毒和细菌基因中存在重叠的诸多例子表明，原核生物中对DNA编码能力的简约利用相对普遍。最近在果蝇中与完全不相关的Gart基因座的一个内含子内发现了一个蛹表皮基因，这表明重叠转录单位在高等生物中也存在。然而，这种现象的普遍程度尚不清楚。我们在此报告果蝇基因组另一个区域中一对反向转录单位的3'末端之间存在的一种截然不同的重叠情况。这个88个碱基对（bp）的基因组区域编码多巴胺脱羧酶（Ddc）信使RNA的3'末端，并且以相反方向编码相邻基因（其功能未知）的3'末端。对这两种转录本在生物体内的时空分布分析表明，两种转录本的高水平表达从未同时出现。然而，在3'转录本表达量最高的睾丸中，检测到了低水平的Ddc转录本。这一结果增加了一种可能性，即体内形成了涉及这两种转录本的杂交分子，或者发生了转录干扰，并具有相应的调控意义。
