Penheiter Kristi L, Washburn Taylor M, Porter Stephanie E, Hoffman Matthew G, Jaehning Judith A
Department of Biochemistry and Molecular Genetics and Molecular Biology Program, University of Colorado, Denver, USA.
Mol Cell. 2005 Oct 28;20(2):213-23. doi: 10.1016/j.molcel.2005.08.023.
The yeast Paf1 complex (Paf1C: Paf1, Cdc73, Ctr9, Rtf1, and Leo1) is associated with RNA Polymerase II (Pol II) at promoters and coding regions of transcriptionally active genes, but transcript abundance for only a small subset of genes is altered by loss of Paf1. By using conditional and null alleles of PAF1 and microarrays, we determined the identity of both primary and secondary targets of the Paf1C. Neither primary nor secondary Paf1C target promoters were responsive to loss of Paf1. Instead, Paf1 loss altered poly(A) site utilization of primary target genes SDA1 and MAK21, resulting in increased abundance of 3'-extended mRNAs. The 3'-extended MAK21 RNA is sensitive to nonsense-mediated decay (NMD), as revealed by its increased abundance in the absence of Upf1. Therefore, although the Paf1C is associated with Pol II at initiation and during elongation, these critical Paf1-dependent changes in transcript abundance are due to alterations in posttranscriptional processing.
酵母Paf1复合物（Paf1C：Paf1、Cdc73、Ctr9、Rtf1和Leo1）在转录活跃基因的启动子和编码区域与RNA聚合酶II（Pol II）相关联，但只有一小部分基因的转录本丰度会因Paf1缺失而改变。通过使用PAF1的条件性和无效等位基因以及微阵列，我们确定了Paf1C的主要和次要靶标的身份。Paf1C的主要和次要靶标启动子均对Paf1缺失无反应。相反，Paf1缺失改变了主要靶标基因SDA1和MAK21的聚腺苷酸化位点利用，导致3'端延长的mRNA丰度增加。如在缺乏Upf1时其丰度增加所揭示的，3'端延长的MAK21 RNA对无义介导的衰变（NMD）敏感。因此，尽管Paf1C在起始和延伸过程中与Pol II相关联，但这些关键的Paf1依赖性转录本丰度变化是由于转录后加工的改变。
