Functional Consequences of Subunit Diversity in RNA Polymerases II and V

• DOI: 10.1016/j.celrep.2012.01.004
• Publication Date: 2012-03-03T14:38:16Z
• Authors: Ek Han Tan; Todd Blevins; Thomas S. Ream; Craig S. Pikaard
• Keywords: Processivity; RNA polymerase III; RNA polymerase II

Multisubunit RNA polymerases IV and V (Pol Pol V) evolved as specialized forms of II that mediate RNA-directed DNA methylation (RdDM) transcriptional silencing transposons, viruses, endogenous repeats in plants. Among the subunits common to Arabidopsis thaliana Pols II, IV, are 93% identical alternative ninth subunits, NRP(B/D/E)9a NRP(B/D/E)9b. The 9a 9b subunit variants incompletely redundant with respect II; whereas double mutants embryo lethal, single viable, yet phenotypically distinct. Likewise, or can associate but is impaired only mutants. Based on genetic molecular tests, we attribute defect RdDM function. Collectively, our results reveal a role for demonstrate diversity generates functionally distinct subtypes V.