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The B-WICH chromatin-remodelling complex regulates RNA polymerase III transcription by promoting Max-dependent c-Myc binding.

Sadeghifar F, Böhm S, Vintermist A, Östlund Farrants AK - Nucleic Acids Res. (2015)

Bottom Line: The novel binding patterns of c-Myc and Max link transcription of 5S rRNA to the Myc/Max/Mxd network.Since B-WICH acts prior to c-Myc and other factors, we propose a model in which the B-WICH complex is required to maintain an open chromatin structure at these RNA polymerase III genes.This is a prerequisite for the binding of additional regulatory factors.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden.

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c-Myc requires the B-WICH complex to remodel chromatin for its function. (A) MNase accessibility of the 5S rDNA using cross-linked chromatin from scrambled cells and c-Myc KD cells analysed by qPCR using the primer pairs depicted in Figure 2A. The gene organisation is depicted above the graph, where the hypersensitive site affected by B-WICH is marked by a bar and the E-box by an X. The graph is based on four independent experiments. (B) qPCR analyses of ChIP experiments of the distribution of the WSTF and SNF2h in scrambled and c-Myc KD cells at the 5S rDNA. The position detected by the primer pairs are marked IGS-U for upstream, promoter for the internal promoter in the gene and IGS-D for downstream. The results are based on four independent experiments and the error bars represent standard deviations. (C) Schematic model of the function of the B-WICH complex in RNA pol III transcription, here depicted at the 5S rDNA.
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Figure 8: c-Myc requires the B-WICH complex to remodel chromatin for its function. (A) MNase accessibility of the 5S rDNA using cross-linked chromatin from scrambled cells and c-Myc KD cells analysed by qPCR using the primer pairs depicted in Figure 2A. The gene organisation is depicted above the graph, where the hypersensitive site affected by B-WICH is marked by a bar and the E-box by an X. The graph is based on four independent experiments. (B) qPCR analyses of ChIP experiments of the distribution of the WSTF and SNF2h in scrambled and c-Myc KD cells at the 5S rDNA. The position detected by the primer pairs are marked IGS-U for upstream, promoter for the internal promoter in the gene and IGS-D for downstream. The results are based on four independent experiments and the error bars represent standard deviations. (C) Schematic model of the function of the B-WICH complex in RNA pol III transcription, here depicted at the 5S rDNA.

Mentions: WSTF knock-down had a greater effect on the factor binding at the 5S rDNA locus than c-Myc or Max knock-down. This led us to investigate the order of events between WSTF and c-Myc in transcriptional activation. To determine whether c-Myc knock-down and the subsequent reduction of histone H3 acetylation lead to a similar remodelling of the chromatin structure as that observed in WSTF KD cells, we performed high-resolution MNase walking. In contrast to WSTF knock-down (Figure 2C), c-Myc knock-down did not result in a changed chromatin structure at the 5S rDNA (Figure 8A). This clearly demonstrates that the B-WICH acts at a step prior to c-Myc. This is further supported by the finding that the binding of the B-WICH complex components WSTF and SNF2h was not compromised in c-Myc KD cells (Figure 8B). WSTF and SNF2h were also present at the 5S rDNA locus in cells treated with the compound 10058-F4 and in Brf1 KD cells (Supplementary Figure S6D). We conclude that the B-WICH complex acts prior to c-Myc in the activation of 5S rRNA transcription. We propose a model in which B-WICH is required for the remodelling of chromatin such that a site, most likely an E-box at the 5S rDNA, becomes accessible for the c-Myc-Max complex (Figure 8C). The c-Myc-Max complex subsequently recruits further factors, such as HATs, to obtain the H3 acetylation that is necessary for transcriptional activation.


The B-WICH chromatin-remodelling complex regulates RNA polymerase III transcription by promoting Max-dependent c-Myc binding.

Sadeghifar F, Böhm S, Vintermist A, Östlund Farrants AK - Nucleic Acids Res. (2015)

c-Myc requires the B-WICH complex to remodel chromatin for its function. (A) MNase accessibility of the 5S rDNA using cross-linked chromatin from scrambled cells and c-Myc KD cells analysed by qPCR using the primer pairs depicted in Figure 2A. The gene organisation is depicted above the graph, where the hypersensitive site affected by B-WICH is marked by a bar and the E-box by an X. The graph is based on four independent experiments. (B) qPCR analyses of ChIP experiments of the distribution of the WSTF and SNF2h in scrambled and c-Myc KD cells at the 5S rDNA. The position detected by the primer pairs are marked IGS-U for upstream, promoter for the internal promoter in the gene and IGS-D for downstream. The results are based on four independent experiments and the error bars represent standard deviations. (C) Schematic model of the function of the B-WICH complex in RNA pol III transcription, here depicted at the 5S rDNA.
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Figure 8: c-Myc requires the B-WICH complex to remodel chromatin for its function. (A) MNase accessibility of the 5S rDNA using cross-linked chromatin from scrambled cells and c-Myc KD cells analysed by qPCR using the primer pairs depicted in Figure 2A. The gene organisation is depicted above the graph, where the hypersensitive site affected by B-WICH is marked by a bar and the E-box by an X. The graph is based on four independent experiments. (B) qPCR analyses of ChIP experiments of the distribution of the WSTF and SNF2h in scrambled and c-Myc KD cells at the 5S rDNA. The position detected by the primer pairs are marked IGS-U for upstream, promoter for the internal promoter in the gene and IGS-D for downstream. The results are based on four independent experiments and the error bars represent standard deviations. (C) Schematic model of the function of the B-WICH complex in RNA pol III transcription, here depicted at the 5S rDNA.
Mentions: WSTF knock-down had a greater effect on the factor binding at the 5S rDNA locus than c-Myc or Max knock-down. This led us to investigate the order of events between WSTF and c-Myc in transcriptional activation. To determine whether c-Myc knock-down and the subsequent reduction of histone H3 acetylation lead to a similar remodelling of the chromatin structure as that observed in WSTF KD cells, we performed high-resolution MNase walking. In contrast to WSTF knock-down (Figure 2C), c-Myc knock-down did not result in a changed chromatin structure at the 5S rDNA (Figure 8A). This clearly demonstrates that the B-WICH acts at a step prior to c-Myc. This is further supported by the finding that the binding of the B-WICH complex components WSTF and SNF2h was not compromised in c-Myc KD cells (Figure 8B). WSTF and SNF2h were also present at the 5S rDNA locus in cells treated with the compound 10058-F4 and in Brf1 KD cells (Supplementary Figure S6D). We conclude that the B-WICH complex acts prior to c-Myc in the activation of 5S rRNA transcription. We propose a model in which B-WICH is required for the remodelling of chromatin such that a site, most likely an E-box at the 5S rDNA, becomes accessible for the c-Myc-Max complex (Figure 8C). The c-Myc-Max complex subsequently recruits further factors, such as HATs, to obtain the H3 acetylation that is necessary for transcriptional activation.

Bottom Line: The novel binding patterns of c-Myc and Max link transcription of 5S rRNA to the Myc/Max/Mxd network.Since B-WICH acts prior to c-Myc and other factors, we propose a model in which the B-WICH complex is required to maintain an open chromatin structure at these RNA polymerase III genes.This is a prerequisite for the binding of additional regulatory factors.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden.

Show MeSH
Related in: MedlinePlus