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The LPS-induced transcriptional upregulation of the chicken lysozyme locus involves CTCF eviction and noncoding RNA transcription.

Lefevre P, Witham J, Lacroix CE, Cockerill PN, Bonifer C - Mol. Cell (2008)

Bottom Line: Expression of LINoCR is correlated with IKKalpha recruitment, histone H3 phosphoacetylation in the transcribed region, the repositioning of a nucleosome over the CTCF binding site, and, eventually, CTCF eviction.Each of these events requires transcription elongation.Our data reveal a transcription-dependent mechanism of chromatin remodeling that switches a cis-regulatory region from a repressive to an active conformation.

View Article: PubMed Central - PubMed

Affiliation: Leeds Institute of Molecular Medicine, University of Leeds, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds LS9 7TF, UK. medple@leeds.ac.uk

ABSTRACT
Transcription of the lysozyme gene is rapidly induced by proinflammatory stimuli such as treatment with bacterial lipopolysaccharide (LPS). Here we show that this induction involves both the relief of repression mediated by the enhancer-blocking protein CTCF that binds to a negative regulatory element at -2.4 kb, and the activation of two flanking enhancer elements. The downstream enhancer has promoter activity, and LPS stimulation initiates the transient synthesis of a noncoding RNA (LINoCR) transcribed through the -2.4 kb element. Expression of LINoCR is correlated with IKKalpha recruitment, histone H3 phosphoacetylation in the transcribed region, the repositioning of a nucleosome over the CTCF binding site, and, eventually, CTCF eviction. Each of these events requires transcription elongation. Our data reveal a transcription-dependent mechanism of chromatin remodeling that switches a cis-regulatory region from a repressive to an active conformation.

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The Lysozyme Gene Is LPS Inducible(A) General organization of the lysozyme locus.(B) Time course of lysozyme mRNA expression in HD11 cells following LPS stimulation. Results are expressed relative to GAPDH expression. Error bars represent ± SD from three independent experiments.
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fig1: The Lysozyme Gene Is LPS Inducible(A) General organization of the lysozyme locus.(B) Time course of lysozyme mRNA expression in HD11 cells following LPS stimulation. Results are expressed relative to GAPDH expression. Error bars represent ± SD from three independent experiments.

Mentions: The chicken lysozyme gene is a well-studied model to investigate the effects of proinflammatory stimuli on gene expression. It is upregulated during macrophage differentiation and reaches its highest expression level in LPS-stimulated macrophages. Transcription is controlled by three enhancers located 6.1, 3.9, and 2.7 kb upstream of the transcription start site, a complex promoter, and a negative regulatory element at −2.4 kb (Bonifer et al., 1997). The −2.4 kb element was shown to have silencer activity via its ability to block the activity of the −2.7 kb enhancer and lysozyme promoter activity independently of its position and orientation (Baniahmad et al., 1987, 1990). Transcription factor recruitment occurs in several steps, with the early acting transcription factors such as NF1 and Fli-1 binding first to the −6.1 and −3.9 kb enhancers, followed by the recruitment of CREB-binding protein (Kontaraki et al., 2000; Lefevre et al., 2003). LPS stimulation leads to an additional recruitment of C/EBPβ and significant alterations in chromatin structure at the enhancers and promoter (Kontaraki et al., 2000; Lefevre et al., 2005, 2003), such as a switch in the pattern of DNase I hypersensitive sites (DHSs). Prior to LPS induction, DHSs are present at the −2.4 kb element and at the −6.1 and −3.9 kb enhancers. Following stimulation, the DHS at the −2.4 kb element disappears, and two new DHSs appear at the −2.7 kb enhancer and at a hormone response element (HRE) at −1.9 kb. In addition, this region contains specifically positioned nucleosomes, which are remodeled after LPS stimulation (Hecht et al., 1988; Huber et al., 1995, 1996; Kontaraki et al., 2000) (Figure 1A). However, neither the exact kinetics of chromatin modification nor the nature of interdependence between these regulatory elements is known.


The LPS-induced transcriptional upregulation of the chicken lysozyme locus involves CTCF eviction and noncoding RNA transcription.

Lefevre P, Witham J, Lacroix CE, Cockerill PN, Bonifer C - Mol. Cell (2008)

The Lysozyme Gene Is LPS Inducible(A) General organization of the lysozyme locus.(B) Time course of lysozyme mRNA expression in HD11 cells following LPS stimulation. Results are expressed relative to GAPDH expression. Error bars represent ± SD from three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2581490&req=5

fig1: The Lysozyme Gene Is LPS Inducible(A) General organization of the lysozyme locus.(B) Time course of lysozyme mRNA expression in HD11 cells following LPS stimulation. Results are expressed relative to GAPDH expression. Error bars represent ± SD from three independent experiments.
Mentions: The chicken lysozyme gene is a well-studied model to investigate the effects of proinflammatory stimuli on gene expression. It is upregulated during macrophage differentiation and reaches its highest expression level in LPS-stimulated macrophages. Transcription is controlled by three enhancers located 6.1, 3.9, and 2.7 kb upstream of the transcription start site, a complex promoter, and a negative regulatory element at −2.4 kb (Bonifer et al., 1997). The −2.4 kb element was shown to have silencer activity via its ability to block the activity of the −2.7 kb enhancer and lysozyme promoter activity independently of its position and orientation (Baniahmad et al., 1987, 1990). Transcription factor recruitment occurs in several steps, with the early acting transcription factors such as NF1 and Fli-1 binding first to the −6.1 and −3.9 kb enhancers, followed by the recruitment of CREB-binding protein (Kontaraki et al., 2000; Lefevre et al., 2003). LPS stimulation leads to an additional recruitment of C/EBPβ and significant alterations in chromatin structure at the enhancers and promoter (Kontaraki et al., 2000; Lefevre et al., 2005, 2003), such as a switch in the pattern of DNase I hypersensitive sites (DHSs). Prior to LPS induction, DHSs are present at the −2.4 kb element and at the −6.1 and −3.9 kb enhancers. Following stimulation, the DHS at the −2.4 kb element disappears, and two new DHSs appear at the −2.7 kb enhancer and at a hormone response element (HRE) at −1.9 kb. In addition, this region contains specifically positioned nucleosomes, which are remodeled after LPS stimulation (Hecht et al., 1988; Huber et al., 1995, 1996; Kontaraki et al., 2000) (Figure 1A). However, neither the exact kinetics of chromatin modification nor the nature of interdependence between these regulatory elements is known.

Bottom Line: Expression of LINoCR is correlated with IKKalpha recruitment, histone H3 phosphoacetylation in the transcribed region, the repositioning of a nucleosome over the CTCF binding site, and, eventually, CTCF eviction.Each of these events requires transcription elongation.Our data reveal a transcription-dependent mechanism of chromatin remodeling that switches a cis-regulatory region from a repressive to an active conformation.

View Article: PubMed Central - PubMed

Affiliation: Leeds Institute of Molecular Medicine, University of Leeds, Wellcome Trust Brenner Building, St. James's University Hospital, Leeds LS9 7TF, UK. medple@leeds.ac.uk

ABSTRACT
Transcription of the lysozyme gene is rapidly induced by proinflammatory stimuli such as treatment with bacterial lipopolysaccharide (LPS). Here we show that this induction involves both the relief of repression mediated by the enhancer-blocking protein CTCF that binds to a negative regulatory element at -2.4 kb, and the activation of two flanking enhancer elements. The downstream enhancer has promoter activity, and LPS stimulation initiates the transient synthesis of a noncoding RNA (LINoCR) transcribed through the -2.4 kb element. Expression of LINoCR is correlated with IKKalpha recruitment, histone H3 phosphoacetylation in the transcribed region, the repositioning of a nucleosome over the CTCF binding site, and, eventually, CTCF eviction. Each of these events requires transcription elongation. Our data reveal a transcription-dependent mechanism of chromatin remodeling that switches a cis-regulatory region from a repressive to an active conformation.

Show MeSH
Related in: MedlinePlus