Unlike nuclear multisubunit RNA polymerases I, II, and III, whose subunit compositions are conserved throughout eukaryotes, plant RNA polymerases IV and V are nonessential, Pol II-related enzymes whose subunit compositions are still evolving. Whereas Arabidopsis Pols IV and V differ from Pol II in four or five of their 12 subunits, respectively, and differ from one another in three subunits, pr...

RNA polymerase I (Pol I) is a 14-subunit enzyme that solely synthesizes pre-ribosomal RNA. Recently, the crystal structure of apo Pol I gave unprecedented insight into its molecular architecture. Here, we present three cryo-EM structures of elongating Pol I, two at 4.0 Å and one at 4.6 Å resolution, and a Pol I open complex at 3.8 Å resolution. Two modules in Pol I mediate the narrowing of the ...

This review discusses recent insights in the roles of DNA polymerases (Pol) delta and epsilon in eukaryotic DNA replication. A growing body of evidence specifies Pol epsilon as the leading strand DNA polymerase and Pol delta as the lagging strand polymerase during undisturbed DNA replication. New evidence supporting this model comes from the use of polymerase mutants that show an asymmetric mut...

Purified RNA polymerase II (pol II) from the yeast Saccharomyces cerevisiae pauses without releasing at many locations during in vitro transcription. Pausing can be induced by intrinsic DNA sequence as well as by specific DNA bound proteins such as the RNA pol I termination factor, Reb1p, or lac repressor. Addition of rho termination factor from E. coli induces RNA pol II to release at all of t...

Although yeast RNA polymerase III (Pol III) and the auxiliary factors TFIIIC and TFIIIB are well characterized, the mechanisms of class III gene regulation are poorly understood. Previous studies identified MAF1, a gene that affects tRNA suppressor efficiency and interacts genetically with Pol III. We show here that tRNA levels are elevated in maf1 mutant cells. In keeping with the higher level...

We have examined the influence of RNA upon the interaction of Gag-Pol with Gag during human immunodeficiency virus type 1 (HIV-1) assembly. COS7 cells were transfected with protease-negative HIV-1 proviral DNA, and Gag/Gag-Pol complexes were detected by coimmunoprecipitation with anti-integrase. In COS7 cells, Gag/Gag-Pol is found almost entirely in pelletable, membrane-bound complexes. Exposur...

RNA polymerase III (Pol III) synthesizes short noncoding RNAs, many of which are essential for translation. Accordingly, Pol III activity is tightly regulated with cell growth and proliferation by factors such as MYC, RB1, TRP53, and MAF1. MAF1 is a repressor of Pol III transcription whose activity is controlled by phosphorylation; in particular, it is inactivated through phosphorylation by the...

During herpes simplex virus infection, expression of the viral DNA polymerase (pol) gene is regulated temporally as an early (beta) gene and is additionally down-regulated at late times at the level of translation (D. R. Yager, A. I. Marcy, and D. M. Coen, J. Virol. 64:2217-2225, 1990). To examine the role of viral DNA synthesis in pol regulation, we studied pol expression during infections in ...

Live cell imaging of mammalian RNA polymerase II (Pol II) has previously relied on random insertions of exogenous, mutant Pol II coupled with the degradation of endogenous Pol II using a toxin, α-amanitin. Therefore, it has been unclear whether over-expression of labeled Pol II under an exogenous promoter may have played a role in reported Pol II dynamics in vivo. Here we label the endogenous P...

Our view of the RNA polymerase III (Pol III) transcription machinery in mammalian cells arises mostly from studies of the RN5S (5S) gene, the Ad2 VAI gene, and the RNU6 (U6) gene, as paradigms for genes with type 1, 2, and 3 promoters. Recruitment of Pol III onto these genes requires prior binding of well-characterized transcription factors. Technical limitations in dealing with repeated genomi...