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Heat shock transcription factor (Hsf)-4b recruits Brg1 during the G1 phase of the cell cycle and regulates the expression of heat shock proteins.
J Cell Biochem. 2006 Aug 15; 98(6):1528-42.JC

Abstract

Human brahma-related gene 1(Brg1) is a subunit of the switching/sucrose non-fermenting (SWI/SNF) chromatin-remodeling complex and regulates transcription during cell growth and differentiation and has been found to be mutated in many types of human cancers. Mammalian heat shock factor 1 (Hsf1), which binds conserved sequences on the promoter of the hsp70 gene when cells are exposed to various stress stimuli, utilizes Brg1-SWI/SNF complexes and stimulates transcription in vitro at the level of initiation and elongation. In contrast to the stress-inducibility of Hsf1, in vitro transcribed/translated Hsf4b binds to the heat shock element (HSE) constitutively and loses its ability to bind HSEs following stress. The regulation of Hsf4b transcriptional activity in vivo remains unclear. Here, we present evidence that Hsf4b recruits Brg1 complexes to the promoters of heat shock proteins (HSPs) under physiological growth conditions. Furthermore, in an asynchronous cell population, the association of Hsf4b with Brg1 complexes is regulated in response to activation/inactivation of the extracellular signal regulated protein kinase 1/2 (ERK1/2) signaling pathway. Since Brg1 is also the target of mitogen-activated protein (MAP) kinases and other protein kinases and it is hyperphosphorylated and inactivated during the G2/M phase of the cell cycle, we tested whether the association of Hsf4b with Brg1 complexes is altered during the cell cycle. The results indicate that association of Hsf4b with Brg1 complexes is undetectable during G2/M; however, an Hsf4b interaction with Brg1 complexes is evident at 1-3 h after progression of cells into G1, where chromatin structure is presumed to be more accessible to transcriptional regulatory proteins. At this time, Hsf4b exhibits increased DNA-binding activity and is detectable on promoters of multiple Hsps. To determine the unique role of Hsf4b in stimulating the expression of Hsps during the cell cycle, experiments were conducted with mouse embryo fibroblasts (MEFs) deficient in individual Hsfs. The results indicate that in the absence of Hsf1 and Hsf2, Hsf4b expression in cells leads to increased ability of Hsf4b to bind HSE during G1, leading to enhanced synthesis of inducible Hsp70.

Authors+Show Affiliations

Tu N
Molecular Chaperone Biology/Radiobiology Program, Medical College of Georgia, Augusta, Georgia 30912, USA.
Hu Y
No affiliation info available
Mivechi NF
No affiliation info available

MeSH

AnimalsCell CycleCells, CulturedChromatin Assembly and DisassemblyDNA HelicasesDNA-Binding ProteinsG1 PhaseHeLa CellsHeat Shock Transcription FactorsHeat-Shock ProteinsHumansMAP Kinase Signaling SystemMiceNuclear ProteinsPromoter Regions, GeneticSignal TransductionTranscription FactorsTransfection

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

16552721

Citation

Tu, Naxin, et al. "Heat Shock Transcription Factor (Hsf)-4b Recruits Brg1 During the G1 Phase of the Cell Cycle and Regulates the Expression of Heat Shock Proteins." Journal of Cellular Biochemistry, vol. 98, no. 6, 2006, pp. 1528-42.
Tu N, Hu Y, Mivechi NF. Heat shock transcription factor (Hsf)-4b recruits Brg1 during the G1 phase of the cell cycle and regulates the expression of heat shock proteins. J Cell Biochem. 2006;98(6):1528-42.
Tu, N., Hu, Y., & Mivechi, N. F. (2006). Heat shock transcription factor (Hsf)-4b recruits Brg1 during the G1 phase of the cell cycle and regulates the expression of heat shock proteins. Journal of Cellular Biochemistry, 98(6), 1528-42.
Tu N, Hu Y, Mivechi NF. Heat Shock Transcription Factor (Hsf)-4b Recruits Brg1 During the G1 Phase of the Cell Cycle and Regulates the Expression of Heat Shock Proteins. J Cell Biochem. 2006 Aug 15;98(6):1528-42. PubMed PMID: 16552721.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Heat shock transcription factor (Hsf)-4b recruits Brg1 during the G1 phase of the cell cycle and regulates the expression of heat shock proteins. AU - Tu,Naxin, AU - Hu,Yanzhong, AU - Mivechi,Nahid F, PY - 2006/3/23/pubmed PY - 2006/12/9/medline PY - 2006/3/23/entrez SP - 1528 EP - 42 JF - Journal of cellular biochemistry JO - J Cell Biochem VL - 98 IS - 6 N2 - Human brahma-related gene 1(Brg1) is a subunit of the switching/sucrose non-fermenting (SWI/SNF) chromatin-remodeling complex and regulates transcription during cell growth and differentiation and has been found to be mutated in many types of human cancers. Mammalian heat shock factor 1 (Hsf1), which binds conserved sequences on the promoter of the hsp70 gene when cells are exposed to various stress stimuli, utilizes Brg1-SWI/SNF complexes and stimulates transcription in vitro at the level of initiation and elongation. In contrast to the stress-inducibility of Hsf1, in vitro transcribed/translated Hsf4b binds to the heat shock element (HSE) constitutively and loses its ability to bind HSEs following stress. The regulation of Hsf4b transcriptional activity in vivo remains unclear. Here, we present evidence that Hsf4b recruits Brg1 complexes to the promoters of heat shock proteins (HSPs) under physiological growth conditions. Furthermore, in an asynchronous cell population, the association of Hsf4b with Brg1 complexes is regulated in response to activation/inactivation of the extracellular signal regulated protein kinase 1/2 (ERK1/2) signaling pathway. Since Brg1 is also the target of mitogen-activated protein (MAP) kinases and other protein kinases and it is hyperphosphorylated and inactivated during the G2/M phase of the cell cycle, we tested whether the association of Hsf4b with Brg1 complexes is altered during the cell cycle. The results indicate that association of Hsf4b with Brg1 complexes is undetectable during G2/M; however, an Hsf4b interaction with Brg1 complexes is evident at 1-3 h after progression of cells into G1, where chromatin structure is presumed to be more accessible to transcriptional regulatory proteins. At this time, Hsf4b exhibits increased DNA-binding activity and is detectable on promoters of multiple Hsps. To determine the unique role of Hsf4b in stimulating the expression of Hsps during the cell cycle, experiments were conducted with mouse embryo fibroblasts (MEFs) deficient in individual Hsfs. The results indicate that in the absence of Hsf1 and Hsf2, Hsf4b expression in cells leads to increased ability of Hsf4b to bind HSE during G1, leading to enhanced synthesis of inducible Hsp70. SN - 0730-2312 UR - https://www.unboundmedicine.com/medline/citation/16552721/Heat_shock_transcription_factor__Hsf__4b_recruits_Brg1_during_the_G1_phase_of_the_cell_cycle_and_regulates_the_expression_of_heat_shock_proteins_ DB - PRIME DP - Unbound Medicine ER -