Department of Cell Biology, University of Medicine and Dentistry of New Jersey, 2 Medical Center Drive, Stratford, New Jersey 08084, USA.
EMBO Rep. 2010 Feb;11(2):106-11. doi: 10.1038/embor.2009.271. Epub 2010 Jan 8.
Most transcripts in growing cells are ribosomal RNA precursors (pre-rRNA). Here, we show that in mammals, aberrant pre-rRNA transcripts generated by RNA polymerase I (Pol I) are polyadenylated and accumulate markedly after treatment with low concentrations of actinomycin D (ActD), which blocks the synthesis of full-length rRNA. The poly(A) polymerase-associated domain-containing protein 5 is required for polyadenylation, whereas the exosome is partly responsible for the degradation of the short aberrant transcripts. Thus, polyadenylation functions in the quality control of Pol I transcription in metazoan cells. The impact of excessive aberrant RNAs on the degradation machinery is an unrecognized mechanism that might contribute to biological properties of ActD.
大多数生长细胞中的转录本是核糖体 RNA 前体（pre-rRNA）。在这里，我们表明在哺乳动物中，由 RNA 聚合酶 I（Pol I）产生的异常 pre-rRNA 转录本被聚腺苷酸化，并在低浓度放线菌素 D（ActD）处理后明显积累，放线菌素 D 可阻止全长 rRNA 的合成。聚腺苷酸化需要含有多聚 A 聚合酶相关结构域的蛋白 5，而外切体部分负责短异常转录本的降解。因此，聚腺苷酸化在真核细胞的 Pol I 转录质量控制中起作用。过多异常 RNA 对降解机制的影响是一种尚未被认识的机制，可能有助于 ActD 的生物学特性。
