H2B

Official Full Name

H2B clustered histone 21

Organism

Homo sapiens

GeneID

8349

Background

Histones are basic nuclear proteins that are responsible for the nucleosome structure of the chromosomal fiber in eukaryotes. Two molecules of each of the four core histones (H2A, H2B, H3, and H4) form an octamer, around which approximately 146 bp of DNA is wrapped in repeating units, called nucleosomes. The linker histone, H1, interacts with linker DNA between nucleosomes and functions in the compaction of chromatin into higher order structures. This gene encodes a replication-dependent histone that is a member of the histone H2B family, and generates two transcripts through the use of the conserved stem-loop termination motif, and the polyA addition motif. The protein has antibacterial and antifungal antimicrobial activity. [provided by RefSeq, Aug 2015]

Synonyms

H2BC21; H2B; H2BE; H2BQ; GL105; H2B.1; H2BFQ; H2BGL105; H2B-GL105; HIST2H2BE;

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Detailed Information

Recent Research Progress

The H2B gene encodes the H2B protein which is a member of the histone family. Related research shows that mono-ubiquitination of H2B (ubH2B) in the histone tail (at Lys-123 in yeast or Lys-120 in humans) is a conserved modification that has been implicated in the regulation of transcription, replication, and DNA repair processes.

Histone H2B ubiquitination plays an important role in transcription regulation, and ubH2B inhibits recruitment of elongation factors. In addition, the splicing factor SART3, which has histone chaperone activity, binds to histones and enhances deubiquitination of H2B by the deubiquitinating enzyme, Usp15. It has recently been reported that ubH2B is enriched at the intron-exon boundaries in yeast, drosophila and humans, suggesting a novel link between ubH2B and co-transcriptional pre-mRNA splicing. It has been shown that H2B K34 ubiquitylation by the mammalian male-specific lethal (MSL) complex (MOF-MSL) is part of the protein networks involved in early steps of transcription elongation.

Histone H2B O-GlcNAcylation is an important posttranslational modification during gene transcription. Recent studies also suggest that histone H2B is O-GlcNAcylated at residue S112 by O-GlcNAc transferase (OGT) in vitro. H2B S112 O-GlcNAcylation fluctuates in response to extracellular glucose through the hexosamine biosynthesis pathway (HBP) and promotes H2B K120 monoubiquitination and transcriptional activation. Here some researchers found that the energy-sensing adenosine-monophosphateactivated protein kinase (AMPK) could suppress histone H2B O-GlcNAcylation.

Some researches proved that phosphorylation of histone H2B at serine 36 (H2BS36) have an effect on fat formation in early period. Some data showed that adipogenic stimuli triggered nuclear translocation of S6K1, leading to H2BS36 phosphorylation and recruitment of enhancer of zeste homolog 2 (EZH2) to histone H3, which mediated trimethylation of H3 at lysine 27 (H3K27). This blocked Wnt gene expression and induced upregulation of proliferator-activated receptor-γ (PPAR γ) and CCAAT/enhancer binding protein-α (C/EBPα), which drived adipogenesis. S6K1, a key downstream effector of the mammalian target of rapamycin (mTOR) signaling pathway, plays a critical role in a number of key catabolic responses, including protein, nucleotide, and lipid synthesis.

H2B Figure 1. Schematic depicting of a role for S6K1 in the transcriptional regulation mediated by H2B phosphorylation and H3 trimethylation. (Sang Ah Yi, et al. 2016).

Several reports show that the Spt-Ada-Gcn5-acetyltransferase (SAGA)-mediated H2B deubiquitination controls the development of neuronal connectivity in the drosophila visual system. Loss of Ataxin-7, a SAGA subunit, reduces H2B ubiquitination and leads to neural and retinal degeneration, impaired movement, and early lethality.

Many studies have reported that reduced ubiquitination of histone H2B (H2Bub1) may create a pro-tumoral microenvironment. And reduced H2Bub1 is associated with colitis and colorectal cancer in humans. H2Bub1, primarily by the ubiquitin ligase (E3) ring finger protein 20 (RNF20), is reduced in many advanced cancers. Notably, colon and colorectal tumors in human ulcerative colitis patient showed downregulation of H2Bub1 and RNF20 in both epithelium and stroma. Tarcic et al. reports that downregulation of H2Bub1 and RNF20 promotes chronic colonic inflammation and inflammation-associated colorectal cancer in mice and humans, partly by augmenting nuclear factor kappa B (NF-kB) activity and attenuating the anti-tumoral T cell response. Downregulation of H2Bub1 and RNF20 favors recruitment of p65-containing NF-kB dimers over repressive p50 homodimers, and decreases the heterochromatin mark histone H3 lysine 9 trimethylation (H3K9me3) on a subset of NF-kB target genes to augment their transcription. What needs to be explained here is that p65 and p50 are subunit of NF-kB transcription factor.

H2B Figure 2. Schematic depicting of downregulation of H2Bub1 and RNF20 promotes chronic colonic inflammation and inflammation-associated colorectal cancer. (Ohad Tarcic, et al. 2016).

Loss of global H2Bub1 detected by immunohistochemical staining has been reported in a number of cancers including breast, colorectal and parathyroid. In the case of parathyroid cancer, a mechanistic explanation for the loss of H2Bub1 is provided by the frequent occurrence of mutations in the tumour suppressor cell division cycle protein 73 homolog (CDC73), leading to the disruption of the RNA polymerase II-associated factor 1 (PAF1) transcriptional complex. Related research shows that basal levels of H2Bub1 were found to be unchanged when comparing normal mammary epithelium with benign breast tumour; however, in malignant and metastatic breast cancer cells, H2Bub1 levels were found to be significantly reduced.

References:

Wu L, et al. H2B ubiquitylation promotes RNA Pol II processivity via PAF1 and pTEFb. Molecular Cell, 2014, 54(6):920-931.
Xu Q, et al. AMPK regulates histone H2B O-GlcNAcylation. Nucleic Acids Research, 2014, 42(9):5594.
Cole A J, et al. Histone H2B monoubiquitination: roles to play in human malignancy. Endocrine-related cancer, 2015, 22(1):T19.
Mohan R D, et al. Loss of Drosophila Ataxin-7, a SAGA subunit, reduces H2B ubiquitination and leads to neural and retinal degeneration. Rare Diseases, 2014, 28(1):259-72.
Tarcic O, et al. RNF20 Links Histone H2B Ubiquitylation with Inflammation and Inflammation-Associated Cancer. Cell Reports, 2016, 14(6):1462-1476.
Sang A Y, et al. S6K1 Phosphorylation of H2B Mediates EZH2 Trimethylation of H3: A Determinant of Early Adipogenesis. Molecular Cell, 2016, 62(3):443-452.
Weake V M, et al. SAGA‐mediated H2B deubiquitination controls the development of neuronal connectivity in the Drosophila visual system. Embo Journal, 2014, 27(2):394-405.
Long L, et al. The U4/U6 recycling factor SART3 has histone chaperone activity and associates with USP15 to regulate H2B deubiquitination. Journal of Biological Chemistry, 2014, 289(13):8916-8930.

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