Plant-unique transcriptional machinery: the Pol IV-RDR2 complex cooperates to synthesize double-stranded RNA

[video: Unique double-stranded RNA synthesis mechanism in plants]

cas.

Transposons were first discovered in maize by American geneticist Barbara McClintock (Nobel Prize in Physiology and Medicine in 1983) and are widely distributed in the genomes of bacteria, viruses and eukaryotes

The RNA-directed DNA methylation (RdDM) pathway is an important pathway for genome methylation in higher plants

Pol IV and Pol V are the fourth and fifth multi-subunit RNA polymerases in eukaryotes, and their gene transcription regions, transcription initiation, elongation and termination mechanisms, and transcriptional regulation are all similar to those of Pol I, Pol II and Pol.

On December 24, 2021, Zhang Yu's research team and Wang Jiawei's research team from the Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, and Feng Yu's team from Zhejiang University jointly published a paper entitled "Pol IV and RDR2: A two-RNA-polymerase" in "Science".

In this work, the authors overcame the bottleneck in the preparation of low-abundance ultra-large protein complexes, purified the endogenous Pol IV-RDR2 complex through the Arabidopsis thaliana suspension cell system, and then analyzed the single-particle reconstitution by cryo-electron microscopy.

The three-dimensional structure supports the evolution of Pol IV from Pol II, however hundreds of millions of years of evolution have made the catalytic center and external building blocks of Pol IV different from Pol II

The most significant finding of this study is that Pol IV and RDR2 form a stable complex, and the catalytic centers of these two polymerases are connected by an internal channel, and the single-stranded RNA synthesized by Pol IV using double-stranded DNA as a template passes through This internal channel is passed directly to RDR2, so that RDR2 can export double-stranded RNA using this single-stranded RNA as a template

　　This work reveals for the first time the three-dimensional architecture of the fourth multi-subunit RNA polymerase in eukaryotes, elucidating the unique molecular mechanism of the cooperative transcription of two RNA polymerases, Pol IV and RDR2, and answering how double-stranded RNA is synthesized in the RdDM pathway scientific issues

　　The paper is co-first authored by Huang Kun, Wu Xiaoxian, Fang Chengli and Xu Zhougao of the Center of Excellence for Molecular Plants, and researcher Zhang Yu, Wang Jiawei and Zhejiang University researcher Feng Yu are co-corresponding authors

　　Paper link: https://　　

　　The three-dimensional structure of Pol IV-RDR2 and the mechanism of their efficient cooperation to synthesize double-stranded RNA