Title: Phosphorylation of Drosophila Brahma on CDK-phosphorylation sites is important for cell cycle regulation and differentiation
Authors: Roesley, SNA
La Marca, JE
Deans, AJ
Mckenzie, L
Suryadinata, R
Burke, P
Portela, M
Wang, HY
Bernard, O
Sarcevic, B
Richardson, HE
Issue Year: 2018
Series Cell Cycle:
Abstract The SWI/SNF ATP-dependent chromatin-remodeling complex is an important evolutionarily conserved regulator of cell cycle progression. It associates with the Retinoblastoma (pRb)/HDAC/E2F/DP transcription complex to modulate cell cycle-dependent gene expression. The key catalytic component of the SWI/SNF complex in mammals is the ATPase subunit, Brahma (BRM) or BRG1. BRG1 was previously shown to be phosphorylated by the G(1)-S phase cell cycle regulatory kinase Cyclin E/CDK2 in vitro, which was associated with the bypass of G(1) arrest conferred by BRG1 expression. However, it is unknown whether direct Cyclin E/CDK2-mediated phosphorylation of BRM/BRG1 is important for G(1)-S phase cell cycle progression and proliferation in vivo. Herein, we demonstrate for the first time the importance of CDK-mediated phosphorylation of Brm in cell proliferation and differentiation in vivo using the Drosophila melanogaster model organism. Expression of a CDK-site phospho-mimic mutant of Brm, brm-ASP (all the potential CDK sites are mutated from Ser/Thr to Asp), which acts genetically as a brm loss-of-function allele, dominantly accelerates progression into the S phase, and bypasses a Retinoblastoma-induced developmental G(1) phase arrest in the wing epithelium. Conversely, expression of a CDK-site phospho-blocking mutation of Brm, brm-ALA, acts genetically as a brm gain-of-function mutation, and in a Brm complex compromised background reduces S phase cells. Expression of the brm phospho-mutants also affected differentiation and Decapentaplegic (BMP/TGF) signaling in the wing epithelium. Altogether our results show that CDK-mediated phosphorylation of Brm is important in G(1)-S phase regulation and differentiation in vivo.Abbreviations: A-P: Anterior-Posterior; BAF: BRG1-associated factor; BMP: Bone Morphogenetic Protein; Brg1: Brahma-Related Gene 1; Brm: Brahma; BSA: Bovine Serum Albumin; CDK: Cyclin dependent kinase dpp: decapentaplegic; EdU: 5-Ethynyl 2'-DeoxyUridine; EGFR: Epidermal Growth Factor Receptor; en: engrailed; GFP: Green Fluorescent Protein; GST: Glutathione-S-Transferase; HDAC: Histone DeACetylase; JNK: c-Jun N-terminal Kinase; Mad: Mothers Against Dpp; MAPK: Mitogen Activated Protein Kinase; MB:: Myelin Basic Protein; nub: nubbin; pH3: phosphorylated Histone H3; PBS: Phosphate Buffered Saline; PBT: PBS Triton; PFA: ParaFormAldehydep; Rb: Retinoblastoma protein; PCV: Posterior Cross-Vein; Snr1: Snf5-Related 1; SWI/SNF: SWitch/Sucrose Non-Fermentable; TGF: Transforming Growth Factor ; TUNEL: TdT-mediated dUTP Nick End Labelling; Wg: Wingless; ZNC: Zone of Non-Proliferating Cells
URI: https://publications.svi.edu.au/publications/4708
Other Identifiers 10.1080/15384101.2018.1493414
Publication type Article