Dynamic and Selective Nucleosome Repositioning during Endotoxin Tolerance

被引:50
作者
El Gazzar, Mohamed [1 ]
Liu, Tiefu
Yoza, Barbara K. [2 ]
McCall, Charles E.
机构
[1] Wake Forest Univ, Bowman Gray Sch Med, Dept Internal Med, Sect Mol Med, Winston Salem, NC 27157 USA
[2] Wake Forest Univ, Bowman Gray Sch Med, Dept Gen Surg, Winston Salem, NC 27157 USA
基金
美国国家卫生研究院;
关键词
NECROSIS-FACTOR-ALPHA; HUMAN MONOCYTIC CELLS; RNA-POLYMERASE-II; NF-KAPPA-B; ASSEMBLY PROTEIN-1; TRANSCRIPTIONAL ACTIVATION; CHROMATIN-STRUCTURE; GENE ACTIVATION; HISTONE H2A.Z; DNA-SEQUENCE;
D O I
10.1074/jbc.M109.067330
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Sepsis is encoded by a sequel of transcription activation and repression events that initiate, sustain, and resolve severe systemic inflammation. The repression/silencing phase occurs in blood leukocytes of animals and humans following the initiation of systemic inflammation due to developing endotoxin tolerance. We previously reported that NF-kappa B transcription factor RelB and histone H3 lysine methyltransferase G9a directly interact to induce facultative heterochromatin assembly and regulate epigenetic silencing during endotoxin tolerance, which is a major feature of sepsis. The general objective of this study was to assess whether dynamic temporal, structural, and positional changes of nucleosomes influence the sepsis phenotype. We used the THP-1 sepsis cell model to isolate mononucleosomes by rapid cell permeabilization and digestion of chromatin with micrococcal nuclease and then compared tumor necrosis factor alpha (TNF alpha) proximal promoter nucleosome alignment in endotoxin-responsive and-tolerant phenotypes. We found differential and dynamic repositioning of nucleosomes from permissive to repressive locations during the activation and silencing phases of transcription reprogramming and identified the following mechanisms that may participate in the process. 1) Two proximal nucleosomes repositioned to expose the primary NF-kappa B DNA binding site in endotoxin-responsive cells, and this "promoter opening" required the ATP-independent chaperone NAP1 to replace the core histone H2A with the H2A.Z variant. 2) During RelB-dependent endotoxin tolerance, the two nucleosomes repositioned and masked the primary NF-kappa B DNA binding site. 3) Small interfering RNA-mediated inhibition of RelB expression prevented repressive nucleosome repositioning and tolerance induction, but the "open" promoter required endotoxin-induced NF-kappa B p65 promoter binding to initiate transcription, supporting the known requirement of p65 posttranslational modifications for transactivation. 4) Sustaining the permissive promoter state after RelB knockdown required ATP-dependent nucleosome remodeler BAF complex. Moreover, we found that forced expression of RelB in responsive cells induced repressive nucleosome positioning and silenced TNF alpha transcription, demonstrating the plasticity of nucleosome remodeling and its dependence on RelB. Our data suggest that nucleosome repositioning controls both the induction and epigenetic silencing phases of TNF alpha transcription associated with sepsis.
引用
收藏
页码:1259 / 1271
页数:13
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