A cryo-EM structure of KTF1-bound polymerase V transcription elongation complex

De novo DNA methylation in plants relies on transcription of RNA polymerase V (Pol V) along with KTF1, which produce long non-coding RNAs for recruitment and assembly of the DNA methylation machinery. Here, we report a cryo-EM structure of the Pol V transcription elongation complex bound to KTF1. The structure reveals the conformation of the structural motifs in the active site of Pol V that accounts for its inferior RNA-extension ability. The structure also reveals structural features of Pol V that prevent it from interacting with the transcription factors of Pol II and Pol IV. The KOW5 domain of KTF1 binds near the RNA exit channel of Pol V providing a scaffold for the proposed recruitment of Argonaute proteins to initiate the assembly of the DNA methylation machinery. The structure provides insight into the Pol V transcription elongation process and the role of KTF1 during Pol V transcription-coupled DNA methylation. Here the authors report the cryo-EM structure of transcription elongation complex comprising eukaryotic RNA polymerase V and its elongation factor KTF1. This work provides structural understanding for the unique function of the fifth member of eukaryotic RNA polymerases.

Automated summary

This study reports the mechanism of de novo DNA methylation in plants. The authors analyze the structure of Pol V and KTF1, revealing the structural motifs in Pol V responsible for its inferior RNA-extension ability, as well as the structural features preventing Pol V from interacting with Pol II and Pol IV transcription factors. The study also finds that the KOW5 domain of KTF1 recruits Argonaute proteins to initiate the assembly of the DNA methylation machinery. This research is important for understanding the transcription elongation process of Pol V and the role of KTF1 in DNA methylation.