Roles for the Histone Modifying and Exchange Complex NuA4 in Cell Cycle Progression in Drosophila melanogaster

Abstract

Robust and synchronous repression of E2F-dependent gene expression is critical to the proper timing of cell cycle exit when cells transition to a postmitotic state. Previously NuA4 was suggested to act as a barrier to proliferation in Drosophila by repressing E2F-dependent gene expression. Here we show that NuA4 activity is required for proper cell cycle exit and the repression of cell cycle genes during the transition to a postmitotic state in vivo. However, the delay of cell cycle exit caused by compromising NuA4 is not due to additional proliferation or effects on E2F activity. Instead NuA4 inhibition results in slowed cell cycle progression through late S and G2 phases due to aberrant activation of an intrinsic p53-independent DNA damage response. A reduction in NuA4 function ultimately produces a paradoxical cell cycle gene expression program, where certain cell cycle genes become derepressed in cells that are delayed during the G2 phase of the final cell cycle. Bypassing the G2 delay when NuA4 is inhibited leads to abnormal mitoses and results in severe tissue defects. NuA4 physically and genetically interacts with components of the E2F complex termed Drosophila, Rbf, E2F and Myb/Multi-vulva class B (DREAM/MMB), and modulates a DREAM/MMB-dependent ectopic neuron phenotype in the posterior wing margin. However, this effect is also likely due to the cell cycle delay, as simply reducing Cdk1 is sufficient to generate a similar phenotype. Our work reveals that the major requirement for NuA4 in the cell cycle in vivo is to suppress an endogenous DNA damage response, which is required to coordinate proper S and G2 cell cycle progression with differentiation and cell cycle gene expression.KEYWORDS DNA damage; proliferation; H2Av; cell cycle checkpoint; cell cycle exit A conserved eukaryotic transcriptional oscillator controls cell cycle gene expression in proliferating cells and underlies the well-studied Cyclin/Cdk cell cycle protein oscillator (Orlando et al. 2008;Oikonomou and Cross 2010). In metazoans, this oscillator depends upon transcriptional activation of several hundred cell cycle genes, initiated by E2F transcription factor complexes followed by E2F inhibition (or degradation) (Shibutani et al. 2008;Zielke et al. 2011;Sadasivam and Decaprio 2013). This generates an oscillation of chromatin opening and closing at cell cycle genes that is thought to properly coordinate G1/S and G2/M gene expression as well as the transition to a noncycling state (Litovchick et al. 2007(Litovchick et al. , 2011Forristal et al. 2014). Disruption of this coordination can affect cell cycle progression by causing inappropriate gene expression (Reis and Edgar 2004;Wen et al. 2008;Forristal et al. 2014). While the oscillation of E2F activity is required for robust cell cycle gene expression Korenjak et al. 2012), E2F complexes are not absolutely essential for cell cycle progression or timely cell cycle exit in Drosophila (Frolov et al. 2001(Frolov et al. , 2005. In the absence of E2F activity there must be E2F-independ...

Atg8a interacts with transcription factor Sequoia to control the expression of autophagy genes in Drosophila

“…Our results support previous findings about the yeast and mammalian homologues of Sequoia, Rph1 and KDM4A respectively which have been shown to negatively regulate the transcription of autophagy genes [32]. Our study also supports previous reports about the role of acetylation and deacetylation of LC3 in mammals [10,[33][34][35][36] and the regulation of autophagy by acetylation [28,37].…”

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Histone variant H2A.Z deposition and acetylation directs the canonical Notch signaling response

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Critical genomic regulation mediated by Enhancer of Polycomb

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