Coupling of RNA polymerase III assembly to cell cycle progression in Saccharomyces cerevisiae

Abstract

Assembly of the RNA polymerases in both yeast and humans is proposed to occur in the cytoplasm prior to their nuclear import. Our previous studies identified a cold-sensitive mutation, rpc128-1007, in the yeast gene encoding the second largest Pol III subunit, Rpc128. rpc128-1007 is associated with defective assembly of Pol III complex and, in consequence, decreased level of tRNA synthesis. Here, we show that rpc128-1007 mutant cells remain largely unbudded and larger than wild type cells. Flow cytometry revealed that most rpc128-1007 mutant cells have G1 DNA content, suggesting that this mutation causes pronounced cell cycle delay in the G1 phase. Increased expression of gene encoding Rbs1, the Pol III assembly/import factor, could counteract G1 arrest observed in the rpc128-1007 mutant and restore wild type morphology of mutant cells. Concomitantly, cells lacking Rbs1 show a mild delay in G1 phase exit, indicating that Rbs1 is required for timely cell cycle progression. Using the double rpc128-1007 maf1Δ mutant in which tRNA synthesis is recovered, we confirmed that the Pol III assembly defect associated with rpc128-1007 is a primary cause of cell cycle arrest. Together our results indicate that impairment of Pol III complex assembly is coupled to cell cycle inhibition in the G1 phase. ARTICLE HISTORY

Cross-regulome profiling of RNA polymerases highlights the regulatory role of polymerase III on mRNA transcription by maintaining local chromatin architecture

“…3G). Moreover, cell cycle genes regulated by Pol III are consistent with the previous observation that Pol III assembly is associated with cell cycle progression [53].…”

Coupling Between Cell Cycle Progression and the Nuclear RNA Polymerases System

“…Moreover, the G1 arrest phenotype is not suppressed after inactivation of Maf1, conditions in which elevated levels of tRNAs are produced ( Pluta et al, 2001 ). Thus, they conclude that impairment of RNA pol III complex assembly, and not decreased tRNA transcription levels, is the primary reason for the G1 arrest observed in the rpc128 mutant ( Płonka et al, 2019 ). Very interestingly, Rbs1 was identified as a substrate of cyclin-dependent kinase Cdc28, the main cell cycle regulator in S. cerevisiae , in a global proteomic approach ( Ubersax et al, 2003 ).…”

“…The assembly of eukaryotic RNA polymerases (RNA pol I, II, and III), is not completely understood although some elements involved in that process has been recently identified. We focus on yeast RNA pol III assembly, as coupling between this assembly process and cell cycle progression has been described ( Płonka et al, 2019 ). The authors had previously isolated and characterized conditional mutants affecting the Rpc128, the second largest RNA pol III subunit.…”

“…Thus, mutants affecting the Rpc53 RNA pol III subunit, which has not been described as involved in assembly, leads to a G1 arrest both in yeast ( Mann et al, 1992 ) and mammals ( Ittmann et al, 1993 ). Moreover, depletion of RPC17 (encoding another RNA pol III subunit), also led to a delay in the G1 phase of the cell cycle ( Gómez-Herreros et al, 2013 ) but, interestingly, RBS1 overexpression did not overcome G1 arrest ( Płonka et al, 2019 ). These results indicate that G1 arrest coupled to defects in RNA Pol III can be mediated by different regulatory inputs.…”

Uncovering the mechanisms of transcription elongation by eukaryotic RNA polymerases I, II, and III

“…Pol III transcription is primarily controlled through three distinct promoters (Type 1, 2, and 3) ( Schramm and Hernandez, 2002 ; Geiduschek and Kassavetis, 2001 ) that recruit different combinations of Pol III TFs ( Acker et al., 2013 ; Huang and Maraia, 2001 ; Arimbasseri et al., 2014 ) and a negative regulator, Maf1 ( Boguta et al., 1997 ). Like Pol I, Pol III’s activity is highly specialized for synthesis of translation machinery; therefore, it is tightly linked to cell proliferation ( Płonka et al., 2019 ).…”