McAndrew M, Graham S, Hartmann C, Clayton C
Zentrum für Molekulare Biologie, Heidelberg, Im Neuenheimer Feld 282, D-69120, Heidelberg, Germany.
Exp Parasitol. 1998 Sep;90(1):65-76. doi: 10.1006/expr.1998.4317.
In trypanosomes, most genes are arranged in polycistronic transcription units. Individual mRNAs are generated by 5'-trans splicing and 3' polyadenylation. Remarkably, no regulation of RNA polymerase II transcription has been detected although many RNAs are differentially expressed during kinetoplastid life cycles. Demonstration of specific class II promoters is complicated by the difficulty in distinguishing between genuine promoter activity and stimulation of trans splicing. Using vectors that were designed to allow the detection of low promoter activities in a transcriptionally silent chromosomal context, we isolated a novel trypanosome RNA polymerase I promoter. We were however unable to detect class II promoter activity in any tested DNA fragment. We also integrated genes which were preceded by a T3 promoter into the genome of cells expressing bacteriophage T3 polymerase: surprisingly, transcription was alpha-amanitin sensitive. One possible interpretation of these results is that in trypanosomes, RNA polymerase II initiation is favored by genomic accessibility and double-strand melting.
在锥虫中，大多数基因排列在多顺反子转录单元中。单个mRNA通过5' - 反式剪接和3' 聚腺苷酸化产生。值得注意的是，尽管许多RNA在动基体生命周期中差异表达，但尚未检测到RNA聚合酶II转录的调控。由于难以区分真正的启动子活性和反式剪接的刺激，特定II类启动子的证明变得复杂。使用设计用于在转录沉默的染色体背景下检测低启动子活性的载体，我们分离出一种新型锥虫RNA聚合酶I启动子。然而，我们在任何测试的DNA片段中都未能检测到II类启动子活性。我们还将带有T3启动子的基因整合到表达噬菌体T3聚合酶的细胞基因组中：令人惊讶的是，转录对α-鹅膏蕈碱敏感。这些结果的一种可能解释是，在锥虫中，RNA聚合酶II的起始受基因组可及性和双链解链的青睐。
