Reductions in Linker Histone Levels Are Tolerated in Developing Spermatocytes but Cause Changes in Specific Gene Expression

Lin, Qingcong; Inselman, Amy L.; Han, Xing; Xu, Hui; Zhang, Weijia; Handel, Mary Ann; Skoultchi, Arthur I.

doi:10.1074/jbc.m400925200

Cited by 49 publications

(46 citation statements)

References 45 publications

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“…This allows H1 to bind at random sites and inhibit transcription. Consistent with this idea, transcription profiling of H1 knock-out cells indicates effects on very few genes when compared with the wild-type cells in mice (25). Along with the transcriptional repression on transiently transfected DNA, H1 overexpression resulted in structural changes of the template as evidenced by reduced restriction enzyme accessibility.…”

Section: Discussionsupporting

confidence: 59%

Altered Histone H1 Stoichiometry and an Absence of Nucleosome Positioning on Transfected DNA

Hebbar

Archer

2008

Journal of Biological Chemistry

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The packaging of DNA with histones to form chromatin represents an important and powerful mechanism to regulate gene expression. Critical aspects of chromatin-specific contributions to gene regulation have been revealed by the comparison of the activities from DNA regulatory elements examined both as transiently transfected reporters and stably integrated reporters organized as chromatin. Using the mouse mammary tumor virus (MMTV) promoter as a model, we probed the structural differences between transiently transfected and stably integrated DNA templates. We demonstrated that all four core histones and the linker histone (H1) are associated with the transient template. However, whereas the core histones were present at a similar stoichiometry between the transient and the stable templates, we found that linker histone H1 molecules are fewer on the transient template. By using supercoiling assay, we show that the transient template shows intermediate levels of nucleosomal assembly. Overexpression of H1 resulted in repression of MMTV transcriptional activity and reduced accessibility to restriction endonucleases on the transient MMTV promoter. However, the addition of exogenous H1 failed to impose a normal chromatin structure on the transient template as measured by micrococcal nuclease digestion pattern. Thus, our results suggest that while transiently transfected DNA acquires a full complement of core histones, the underrepresentation of H1 on the transient template is indicative of structural differences between the two templates that may underlie the differences in the mechanisms of activation of the two templates.Transcriptional regulation of eukaryotic promoters is extensively studied by using transient transfection reporter assays. Although these assays have given abundant information on transcription factor binding sites and the effects of various treatments on transcription, it is undetermined how closely they emulate the activity of endogenous promoters. One of the main concerns about using transient transfection to assay promoter activity is the lack of proper chromatin architecture on this DNA (1). This seems particularly important given the impact of chromatin, histone modifications, and chromatin remodeling proteins on transcriptional regulation.Using the glucocorticoid-responsive mouse mammary tumor virus (MMTV) 2 promoter as a model promoter, previous work has demonstrated very clear differences between the stably integrated, replicating copies of the promoter and transiently transfected promoter DNA (2). The MMTV promoter is activated by the hormone-bound glucocorticoid receptor (GR). Although both the stable and the transient MMTV promoters are dependent on hormone for transcriptional activity, accessibility to restriction endonucleases on the promoter is hormoneinducible on the stable template and constitutively accessible on the transient template. This architectural difference was attributed to the lack of proper nucleosomal organization on the transient template as assayed by micrococcal nu...

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Section: Discussionsupporting

confidence: 59%

Altered Histone H1 Stoichiometry and an Absence of Nucleosome Positioning on Transfected DNA

Hebbar

Archer

2008

Journal of Biological Chemistry

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“…In addition, recent studies using electrospray mass spectrometry demonstrate that prolonged glucocorticoid treatment leads to dephosphorylation of specific histone H1 isoforms in mouse cells (Banks et al 2001). While in vivo data as to the effects of linker histone H1 in NR-mediated gene regulation are still lacking, linker histones are essential for mouse development and play a role in spermatogenesis, biological processes known to be regulated by NRs (Fan & Skoultchi 2003, Lin Q. et al 2004. In particular, inactivation of three mouse histone H1 isoforms (H1·2, Figure 2 Model for the role of the ubiquitin-proteasome system in NR-mediated chromatin structure modification and transcriptional regulation.…”

Section: Ubiquitin-proteasome and Nr-dependent Chromatin Remodeling: mentioning

confidence: 99%

Linking the ubiquitin–proteasome pathway to chromatin remodeling/modification by nuclear receptors

Kinyamu

Chen²,

Archer

2005

Journal of Molecular Endocrinology

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Over 25 years ago, eukaryotic cells were shown to contain a highly specific system for the selective degradation of short-lived proteins, this system is known as the ubiquitin-proteasome pathway. In this pathway, proteins are targeted for degradation by covalent modification by a small highly conserved protein named ubiquitin. Ubiquitin-mediated degradation of regulatory proteins plays an important role in numerous cell processes, including cell cycle progression, signal transduction and transcriptional regulation. Recent experiments have shown that the ubiquitin-proteasome pathway is also involved in nuclear hormone receptor (NR)-mediated transcriptional regulation. The idea that the ubiquitinproteasome pathway is involved in NR-mediated transcription is strengthened by experiments showing that ubiquitinproteasome components are recruited to NR target gene promoters. However, it is not clear how these components modulate NR-mediated chromatin remodeling and gene expression. In this review, we postulate the role of the ubiquitin-proteasome pathway on NR-mediated chromatin remodeling and gene regulation based on the current knowledge from studies implicating the pathway in chromatin structure modifications that are applicable to NR function. Since evidence from this laboratory, using the glucocorticoid receptor responsive mouse mammary tumor virus (MMTV) promoter organized as chromatin, suggest that the ubiquitin-proteasome system may be involved in the elongation phase of transcription, we particularly concentrate on chromatin modifications associated with the elongation phase.

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“…However, other studies suggest that H1 can have both positive and negative effects on gene expression (Shen and Gorovsky 1996;Lin et al 2004;Fan et al 2005). To test the role of H1 on transcriptional silencing in vivo in Drosophila, we analyzed the effect of H1 depletion on PEV.…”

Section: Linker Histone H1 Is Essential For Drosophila Developmentmentioning

confidence: 99%

Linker histone H1 is essential for Drosophila development, the establishment of pericentric heterochromatin, and a normal polytene chromosome structure

Lu¹,

Wontakal²,

Emelyanov³

et al. 2009

Genes Dev.

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131

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We generated mutant alleles of Drosophila melanogaster in which expression of the linker histone H1 can be down-regulated over a wide range by RNAi. When the H1 protein level is reduced to ;20% of the level in wildtype larvae, lethality occurs in the late larval -pupal stages of development. Here we show that H1 has an important function in gene regulation within or near heterochromatin. It is a strong dominant suppressor of position effect variegation (PEV). Similar to other suppressors of PEV, H1 is simultaneously involved in both the repression of euchromatic genes brought to the vicinity of pericentric heterochromatin and the activation of heterochromatic genes that depend on their pericentric localization for maximal transcriptional activity. Studies of H1-depleted salivary gland polytene chromosomes show that H1 participates in several fundamental aspects of chromosome structure and function. First, H1 is required for heterochromatin structural integrity and the deposition or maintenance of major pericentric heterochromatin-associated histone marks, including H3K9Me 2 and H4K20Me 2 . Second, H1 also plays an unexpected role in the alignment of endoreplicated sister chromatids. Finally, H1 is essential for organization of pericentric regions of all polytene chromosomes into a single chromocenter. Thus, linker histone H1 is essential in Drosophila and plays a fundamental role in the architecture and activity of chromosomes in vivo.[Keywords: Linker histone H1; heterochromatin; histone methylation; polytene chromosomes; chromocenter; position effect variegation] Supplemental material is available at http://www.genesdev.org. The genomes of eukaryotes are packaged into a highly compact nucleoprotein complex called chromatin. The histones constitute a family of proteins that are intimately involved in organizing chromatin structure. There are five major classes of histones: the core histones H2A, H2B, H3, and H4, and the linker histones usually referred to as H1. The nucleosome core particle is the highly conserved repetitive unit of chromatin organization. It consists of an octamer of the four core histones around which ;145 base pairs (bp) of DNA are wrapped and protected from nuclease digestion (Van Holde 1988;Wolffe 1998). The linker histone H1 binds to core particles and protects an additional ;20 bp of DNA (linker DNA). In metazoans, the abundance of linker histones, although variable during development, approaches that of core histones (Woodcock et al. 2006), suggesting that they play an important role in establishing and maintaining the structure of the chromatin fiber.Much of our knowledge about the roles of linker histones comes from in vitro studies. These studies indicate that two principal functions of linker histones are to stabilize the DNA entering and exiting the core particle and to facilitate the folding of nucleosome arrays into more compact structures (Ramakrishnan 1997;Wolffe 1997). H1 also affects nucleosome core particle spacing and mobility. In vitro studies also suggest that H1 acts pri...

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Reductions in Linker Histone Levels Are Tolerated in Developing Spermatocytes but Cause Changes in Specific Gene Expression

Cited by 49 publications

References 45 publications

Altered Histone H1 Stoichiometry and an Absence of Nucleosome Positioning on Transfected DNA

Altered Histone H1 Stoichiometry and an Absence of Nucleosome Positioning on Transfected DNA

Linking the ubiquitin–proteasome pathway to chromatin remodeling/modification by nuclear receptors

Linker histone H1 is essential for Drosophila development, the establishment of pericentric heterochromatin, and a normal polytene chromosome structure

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