Cheng Y, Gvakharia B, Hardin P E
Department of Biology, Texas A&M University, College Station, Texas 77843, USA.
Mol Cell Biol. 1998 Nov;18(11):6505-14. doi: 10.1128/MCB.18.11.6505.
The period (per) and timeless (tim) genes encode key components of the circadian oscillator in Drosophila melanogaster. The per gene is thought to encode three transcripts via differential splicing (types A, B, and C) that give rise to three proteins. Since the three per mRNA types were based on the analysis of cDNA clones, we tested whether these mRNA types were present in vivo by RNase protection assays and reverse transcriptase-mediated PCR. The results show that per generates two transcript types that differ only by the presence (type A) or absence (type B') of an alternative intron in the 3' untranslated region. Transgenic flies containing transgenes that produce only type B' transcripts (perB'), type A transcripts (perA), or both transcripts (perG) rescue locomotor activity rhythms with average periods of 24.7, 25.4, and 24.4 h, respectively. Although no appreciable differences in type A and type B' mRNA cycling were observed, a slower accumulation of PER in flies making only type A transcripts suggests that the intron affects the translation of per mRNA.
周期（per）基因和无时间（tim）基因编码黑腹果蝇昼夜节律振荡器的关键组分。per基因被认为通过可变剪接产生三种转录本（A、B和C型），进而产生三种蛋白质。由于这三种per mRNA类型是基于cDNA克隆分析得出的，我们通过核糖核酸酶保护分析和逆转录酶介导的聚合酶链反应来检测这些mRNA类型在体内是否存在。结果表明，per产生两种转录本类型，它们仅在3'非翻译区是否存在可变内含子上有所不同（A 型存在，B'型不存在）。含有仅产生B'型转录本（perB'）、A型转录本（perA）或两种转录本（perG）的转基因果蝇分别以平均24.7、25.4和24.4小时的周期拯救了运动活动节律。尽管未观察到A型和B'型mRNA循环有明显差异，但仅产生A型转录本的果蝇中PER积累较慢，这表明内含子影响per mRNA的翻译。
