Abstract
The evolutionarily conserved multifunctional polymerase-associated factor 1 (Paf1) complex (Paf1C), which is composed of at least five subunits (Paf1, Leo1, Ctr9, Cdc73, and Rtf1), plays vital roles in gene regulation and has connections to development and human diseases. Here, we report two structures of each of the human and yeast Ctr9/Paf1 subcomplexes, which assemble into heterodimers with very similar conformations, revealing an interface between the tetratricopeptide repeat module in Ctr9 and Paf1. The structure of the Ctr9/Paf1 subcomplex may provide mechanistic explanations for disease-associated mutations in human PAF1 and CTR9. Our study reveals that the formation of the Ctr9/Paf1 heterodimer is required for the assembly of yeast Paf1C, and is essential for yeast viability. In addition, disruption of the interaction between Paf1 and Ctr9 greatly affects the level of histone H3 methylation in vivo. Collectively, our results shed light on Paf1C assembly and functional regulation.
Highlights
The evolutionarily conserved multifunctional polymerase-associated factor 1 (Paf1) complex (Paf1C), which is composed of at least five subunits (Paf[1], Leo[1], Ctr[9], Cdc[73], and Rtf1), plays vital roles in gene regulation and has connections to development and human diseases
Structural and biochemical data reveal that LEO1 binds to human PAF1C through PAF1 and that the CTR9 subunit is the key scaffold protein in assembling PAF1C46
We confirmed that the human CTR9, PAF1, and LEO1 subunits interacted by showing that three thioredoxin (Trx)-tagged fusion proteins [aa 1–284, Trx-CTR9 (1–284), Trx-PAF1, and Trx-LEO1] eluted from the size-exclusion column as a tripartite complex (Supplementary Fig. 1a)
Summary
The evolutionarily conserved multifunctional polymerase-associated factor 1 (Paf1) complex (Paf1C), which is composed of at least five subunits (Paf[1], Leo[1], Ctr[9], Cdc[73], and Rtf1), plays vital roles in gene regulation and has connections to development and human diseases. 1234567890():,; The highly conserved eukaryotic multifunctional polymerase-associated factor 1 (Paf1) complex (Paf1C) was originally identified in budding yeast over 2 decades ago[1], and robust data suggested that it plays a vital role in transcriptional elongation and chromatin modifications[2,3]. In addition to its interactions with pol II, Paf1C has extensive genetic and physical links to yeast elongation factors Spt4/Spt[5], Spt16/Pob[3], and Dst[1] (corresponding to human DSIF, FACT, and TFIIS/SII, respectively)[4,6,8], allowing it to regulate transcription elongation procession. There is no atomic structure information has been reported about CTR9, which contains multimotifs for protein–protein interaction (Fig. 1a)
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