Interaction of the Jhd2 Histone H3 Lys-4 Demethylase with Chromatin Is Controlled by Histone H2A Surfaces and Restricted by H2B Ubiquitination

Chromatin accessibility: biological functions, molecular mechanisms and therapeutic application

The dynamic regulation of chromatin accessibility is one of the prominent characteristics of eukaryotic genome. The inaccessible regions are mainly located in heterochromatin, which is multilevel compressed and access restricted. The remaining accessible loci are generally located in the euchromatin, which have less nucleosome occupancy and higher regulatory activity. The opening of chromatin is the most important prerequisite for DNA transcription, replication, and damage repair, which is regulated by genetic, epigenetic, environmental, and other factors, playing a vital role in multiple biological progresses. Currently, based on the susceptibility difference of occupied or free DNA to enzymatic cleavage, solubility, methylation, and transposition, there are many methods to detect chromatin accessibility both in bulk and single-cell level. Through combining with high-throughput sequencing, the genome-wide chromatin accessibility landscape of many tissues and cells types also have been constructed. The chromatin accessibility feature is distinct in different tissues and biological states. Research on the regulation network of chromatin accessibility is crucial for uncovering the secret of various biological processes. In this review, we comprehensively introduced the major functions and mechanisms of chromatin accessibility variation in different physiological and pathological processes, meanwhile, the targeted therapies based on chromatin dynamics regulation are also summarized.

Genome-wide identification and expression analysis of the JMJ-C gene family in melon (Cucumis melo L.) reveals their potential role in fruit development

BACKGROUND

Proteins with the jumonji (JMJ)-C domain belong to the histone demethylase family and contribute to reverse histone methylation. Although JMJ-C family genes have an essential role in regulating plant growth and development, the characterization of the JMJ-C family genes in melon has not been uncovered.

RESULTS

In this study, a total of 17 JMJ-C proteins were identified in melon (Cucumis melo L.). CmJMJs were categorized into five subfamilies based on the specific conserved domain: KDM4/JHDM3, KDM5/JARID1, JMJD6, KDM3/JHDM2, and JMJ-C domain-only. The chromosome localization analyses showed that 17 CmJMJs were distributed on nine chromosomes. Cis-acting element analyses of the 17 CmJMJ genes showed numerous hormone, light, and stress response elements distributed in the promoter region. Covariance analysis revealed one pair of replicated fragments (CmJMJ3a and CmJMJ3b) in 17 CmJMJ genes. We investigated the expression profile of 17 CmJMJ genes in different lateral organs and four developmental stages of fruit by RNA-seq transcriptome analysis and RT-qPCR. The results revealed that most CmJMJ genes were prominently expressed in female flowers, ovaries, and developing fruits, suggesting their active role in melon fruit development. Subcellular localization showed that the fruit-related CmJMJ5a protein is specifically localized in the cell nucleus.

CONCLUSIONS

This study provides a comprehensive understanding of the gene structure, classification, and evolution of JMJ-C in melon and supports the clarification of the JMJ-C functions in further research.

Ready, SET, Go: Post-translational regulation of the histone lysine methylation network in budding yeast

Histone lysine methylation is a key epigenetic modification that regulates eukaryotic transcription. Here, we comprehensively review the function and regulation of the histone methylation network in the budding yeast and model eukaryote, Saccharomyces cerevisiae. First, we outline the lysine methylation sites that are found on histone proteins in yeast (H3K4me1/2/3, H3K36me1/2/3, H3K79me1/2/3, and H4K5/8/12me1) and discuss their biological and cellular roles. Next, we detail the reduced but evolutionarily conserved suite of methyltransferase (Set1p, Set2p, Dot1p, and Set5p) and demethylase (Jhd1p, Jhd2p, Rph1p, and Gis1p) enzymes that are known to control histone lysine methylation in budding yeast cells. Specifically, we illustrate the domain architecture of the methylation enzymes and highlight the structural features that are required for their respective functions and molecular interactions. Finally, we discuss the prevalence of post-translational modifications on yeast histone methylation enzymes and how phosphorylation, acetylation, and ubiquitination in particular are emerging as key regulators of enzyme function. We note that it will be possible to completely connect the histone methylation network to the cell's signaling system, given that all methylation sites and cognate enzymes are known, most phosphosites on the enzymes are known, and the mapping of kinases to phosphosites is tractable owing to the modest set of protein kinases in yeast. Moving forward, we expect that the rich variety of post-translational modifications that decorates the histone methylation machinery will explain many of the unresolved questions surrounding the function and dynamics of this intricate epigenetic network.

Histone modifications associated with gene expression and genome accessibility are dynamically enriched at Plasmodium falciparum regulatory sequences

Background

The malaria parasite Plasmodium falciparum has an unusually euchromatic genome with poorly conserved positioning of nucleosomes in intergenic sequences and poorly understood mechanisms of gene regulation. Variant histones and histone modifications determine nucleosome stability and recruit trans factors, but their combinatorial contribution to gene regulation is unclear.

Results

Here, we show that the histone H3 acetylations H3K18ac and H3K27ac and the variant histone Pf H2A.Z are enriched together at regulatory sites upstream of genes. H3K18ac and H3K27ac together dynamically mark regulatory regions of genes expressed during the asexual life cycle. In contrast, H3K4me1 is depleted in intergenic sequence and dynamically depleted upstream of expressed genes. The temporal pattern of H3K27ac and H3K18ac enrichment indicates that they accumulate during S phase and mitosis and are retained at regulatory sequences until at least G1 phase and after cessation of expression of the cognate genes. We integrated our ChIPseq data with existing datasets to show that in schizont stages H3K18ac, H3K27ac and Pf H2A.Z colocalise with the transcription factor PfAP2-I and the bromodomain protein PfBDP1 and are enriched at stably positioned nucleosomes within regions of exposed DNA at active transcriptional start sites. Using transient transfections we showed that sequences enriched with colocalised H3K18ac, H3K27ac and Pf H2A.Z possess promoter activity in schizont stages, but no enhancer-like activity.

Conclusions

The dynamic H3 acetylations define P. falciparum regulatory sequences and contribute to gene activation. These findings expand the knowledge of the chromatin landscape that regulates gene expression in P. falciparum.

Histone lysine methylation and congenital heart disease: From bench to bedside (Review)

Histone post-translational modifications (PTM) as one of the key epigenetic regulatory mechanisms that plays critical role in various biological processes, including regulating chromatin structure dynamics and gene expression. Histone lysine methyltransferase contributes to the establishment and maintenance of differential histone methylation status, which can recognize histone methylated sites and build an association between these modifications and their downstream processes. Recently, it was found that abnormalities in the histone lysine methylation level or pattern may lead to the occurrence of many types of cardiovascular diseases, such as congenital heart disease (CHD). In order to provide new theoretical basis and targets for the treatment of CHD from the view of developmental biology and genetics, this review discusses and elaborates on the association between histone lysine methylation modifications and CHD.

Histone demethylase JMJD2C: epigenetic regulators in tumors

Histone methylation is one of the major epigenetic modifications, and various histone methylases and demethylases participate in the epigenetic regulating. JMJD2C has been recently identified as one of the histone lysine demethylases. As one member of the Jumonji-C histone demethylase family, JMJD2C has the ability to demethylate tri- or di-methylated histone 3 and 2 in either K9 (lysine residue 9) or K36 (lysine residue 36) sites by an oxidative reaction, thereby affecting heterochromatin formation, genomic imprinting, X-chromosome inactivation, and transcriptional regulation of genes. JMJD2C was firstly found to involve in embryonic development and stem cell regulation. Afterwards, aberrant status of JMJD2C histone methylation was observed during the formation and development of various tumors, and it has been reported to play crucial roles in the progression of breast cancer, prostate carcinomas, osteosarcoma, blood neoplasms and so on, indicating that JMJD2C represents a promising anti-cancer target. In this review, we will focus on the research progress and prospect of JMJD2C in tumors, and provide abundant evidence for the functional application and therapeutic potential of targeting JMJD2C in tumors.

Counteracting H3K4 methylation modulators Set1 and Jhd2 co-regulate chromatin dynamics and gene transcription

Histone H3K4 methylation is connected to gene transcription from yeast to humans, but its mechanistic roles in transcription and chromatin dynamics remain poorly understood. We investigated the functions for Set1 and Jhd2, the sole H3K4 methyltransferase and H3K4 demethylase, respectively, in S. cerevisiae. Here, we show that Set1 and Jhd2 predominantly co-regulate genome-wide transcription. We find combined activities of Set1 and Jhd2 via H3K4 methylation contribute to positive or negative transcriptional regulation. Providing mechanistic insights, our data reveal that Set1 and Jhd2 together control nucleosomal turnover and occupancy during transcriptional co-regulation. Moreover, we find a genome-wide co-regulation of chromatin structure by Set1 and Jhd2 at different groups of transcriptionally active or inactive genes and at different regions within yeast genes. Overall, our study puts forth a model wherein combined actions of Set1 and Jhd2 via modulating H3K4 methylation-demethylation together control chromatin dynamics during various facets of transcriptional regulation.

Light-induced nuclear export reveals rapid dynamics of epigenetic modifications

We engineered a photoactivatable system for rapidly and reversibly exporting proteins from the nucleus by embedding a nuclear export signal in the LOV2 domain from phototropin 1. Fusing the chromatin modifier Bre1 to the photoswitch, we achieved light-dependent control of histone H2B monoubiquitylation in yeast, revealing fast turnover of the ubiquitin mark. Moreover, this inducible system allowed us to dynamically monitor the status of epigenetic modifications dependent on H2B ubiquitylation.