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PubMed2025

CRISPRoff epigenome editing for programmable gene silencing in human cell lines and primary T cells.

The advent of CRISPR-based technologies has enabled the rapid advancement of programmable gene manipulation in cells, tissues, and whole organisms. An emerging platform for targeted gene perturbation is epigenetic editing, the direct editing of chemical modifications on DNA and histones that ultimately results in repression or activation of the targeted gene. In contrast to CRISPR nucleases, epigenetic editors modulate gene expression without inducing DNA breaks or altering the genomic sequence of host cells. Recently, we developed the CRISPRoff epigenetic editing technology that simultaneously establishes DNA methylation and repressive histone modifications at targeted gene promoters. Transient expression of CRISPRoff and the accompanying single guide RNAs in mammalian cells results in transcriptional repression of targeted genes that is memorized heritably by cells through cell division and differentiation. Here, we describe our protocol for the delivery of CRISPRoff through plasmid DNA transfection, as well as the delivery of CRISPRoff mRNA, into transformed human cell lines and primary immune cells. We also provide guidance on evaluating target gene silencing and highlight key considerations when utilizing CRISPRoff for gene perturbations. Our protocols are broadly applicable to other CRISPR-based epigenetic editing technologies, as programmable genome manipulation tools continue to evolve rapidly.

Humans↗
PubMed1975

Modification of histone binding in calf thymus chromatin by protamine.

When calf thymus chromatin is incubated with protamine, the protein binds to DNA, forming a chromatin-protamine complex. The binding reaches a saturating level at the weight ratio of protamine to DNA of approximately 0.5. Although the saturated binding of protamine to DNA does not cause major displacement of histones from calf thymus chromatin, examination of the dissociation profiles by salt in combination with urea of protamine-treated chromatin shows that the histone-DNA interactions are markedly altered by such binding. The dissociation of histones from the chromatin-protamine complex requires less NaCl but the same concentration of urea as that for untreated chromatin, suggesting that the electorstatic interactions between the histones and DNA are decreased as a result of protamine binding. When protamine concentration is increased beyond that required for saturated binding to DNA during in vitro exposure of calf thymus chromatin to protamine, lysine-rich histone is completely displaced.

Animals↗
PubMed1970

Modification of histones during spermiogenesis in trout: a molecular mechanism for altering histone binding to DNA.

At a late stage of spermatogenesis in rainbow-trout testis, the entire complement of histones is replaced by newly synthesized protamine and histones are extensively phosphorylated and acetylated. Tryptic digestion of purified histones labeled by incubation of testicular cells with [(32)P]phosphate shows that phosphorylation occurs at a small number of seryl residues. Histone I (lysine-rich) is phosphorylated in the sequence Lys-Ser(PO(4))-Pro-Lys, which is located in the lysine-rich C-terminal region of the molecule. Histones IIb(1) (slightly lysine-rich) and IV (glycine, arginine-rich) give rise to the same phosphopeptide, Ac-Ser(PO(4))-Gly-Arg, which comprises the amino terminus of each histone. Thermolysin digests of phosphohistones IIb(1) and IV also released a phosphopeptide with composition corresponding to the first six residues of histone IV: Ac-Ser(PO(4))-Gly-Arg-Gly-Lys-Gly. An alpha-helical model of the N-terminal region of histone IV shows that this region is a possible DNA-binding site. Phosphorylation at serine 1 together with epsilon-amino acetylation at lysines 5, 8, 12, and 16 (observed in histone IV from trout testis) could profoundly modify ionic interactions and lead to an "unzipping" of histone IV from DNA

Animals↗
PubMed1972

Synthesis, acetylation, and phosphorylation of histone IV and its binding to DNA during spermatogenesis in trout.

During spermatogenesis in trout testis, histone IV is extensively modified by acetylation and phosphorylation. To examine the relationship of synthesis of histone IV to its modification, histone IV labeled with [(3)H]aminoacids and inorganic [(32)P]phosphate was prepared from testis cells by acid extraction and column chromatography. Purified histone IV was resolved by starch gel electrophoresis into 10 bands, of which nine are modified by acetylation and/or phosphorylation. In the first 4 hr of labeling, the diacetyl-histone IV band showed the highest proportion of [(3)H]aminoacid label. After 12 hr of incorporation, more label was found in the triacetyl and tetraacetyl bands. A significant amount of amino-acid label in the two major bands (the unsubstituted and monoacetyl bands) of histone IV was not seen until 16 hr of incubation. From 1 to 12 days, the proportion of label in the unsubstituted and monoacetylated bands increased, while that in the tetra-, tri-, and monoacetyl bands decreased. Very little [(3)H]aminoacid was found in the phosphorylated bands of histone IV in the first 12 hr. However, after 16 hr about 20% of the total (3)H was found in the phosphorylated bands. The proportion increased to 33% and remained at this level between 1 and 8 days, but, by 16 days, had decreased to 12% of the total. These data suggest that an "obligatory" acetylation of recently synthesized histone IV is involved in the correct binding of newly synthesized histone IV to DNA. We propose that epsilon-amino acetylation of lysyl residues 5, 8, 12, and 16 neutralizes their positive charges and allows the NH(2)-terminal region of histone IV to assume the correct conformation (in this case, an alpha-helix), and fit into the major groove of DNA. Deacetylation then "locks" histone IV to DNA by ionic linkages. The biological significance of phosphorylation of histone IV is not known.

Acetates↗
PubMed1984

DNA repair-associated ADP-ribosylation in vivo. Modification of histone H1 differs from that of the principal acceptor proteins.

ADP-ribosylation in vivo of histone H1 was studied in hepatoma cells (Yoshida AH 7974) after treatment with the alkylating agent dimethyl sulfate for 30 min and compared with that of other polypeptides. In unstimulated cells, histone H1 was only a minor acceptor (less than 4%) of total monomeric and polymeric ADP-ribosyl residues. Induction of DNA repair by dimethyl sulfate treatment increased total mono(ADP-ribosyl) protein conjugates 1.6-fold whereas histone H1-linked mono(ADP-ribosyl) groups were elevated greater than 30-fold, thus accounting for nearly one-fourth of the net increase in monomeric ADP-ribosyl residues. In contrast, histone H1-associated poly(ADP-ribosyl) residues comprised only 2% of the total increase in poly(ADP-ribose). The extent to which the histone H1 population became ADP-ribosylated was low even in dimethyl sulfate-treated cells. Less than 2% of the histone H1 molecules were mono(ADP-ribosyl)ated and only 0.003% carried poly(ADP-ribosyl) chains when an average chain length of 10 is assumed. The principal polypeptide acceptors of alkylation-induced ADP-ribosylation were concentrated in two peaks, one migrating close to the position of core histones H3/H2B and accepting most of the induced mono(ADP-ribosyl) and poly(ADP-ribosyl) residues. The other (Mr = 110,000-160,000) resembled auto-modified poly(ADP-ribose) polymerase. Our data demonstrate marked differences of alkylation-induced (ADP-ribosyl)n protein patterns to analyses performed in vitro.

Adenosine Diphosphate Ribose↗
PubMed2025

ChIPmentation for Epigenomic Analysis in Fission Yeast.

Histone modifications and transcription factor-DNA interactions regulate vital processes such as transcription, recombination, repair, and accurate chromosome segregation. Chromatin immunoprecipitation followed by sequencing (ChIP-Seq) has been instrumental in studying genome-wide distribution of DNA-bound or chromatin-associated factors and histone posttranslational modifications (PTMs). Here, we describe a ChIPmentation protocol adapted for fission yeast, Schizosaccharomyces pombe. This method merges Tn5 mediated tagmentation with existing ChIP protocols, resulting in lower sample input requirements with significant reduction in hands-on time and sample preparation costs.

Schizosaccharomyces↗
PubMed2026

Somatic genetic alterations in pituitary neuroendocrine tumors.

The molecular characterization of pituitary neuroendocrine tumors (PitNETs) has progressed pronouncedly in recent years, unraveling the molecular pathways driving initiation and progression of different PitNET types and allowing a better understanding of their biology. The most frequent recurring somatic driver alterations were recognized in corticotroph PitNETs (USP8, USP48, BRAF) and somatotroph PitNETs (GNAS) and, much less frequently, in lactotroph PitNETs (SF3B1). Additional well-characterized somatic driver alterations, including TP53, ATRX, and DAXX, are enriched in aggressive corticotroph tumors. Identification of new molecular markers and delineation of their clinical phenotypes are enabling further subclassification of PitNETs based on tumor molecular profiles, with earlier recognition of more aggressive variants. These molecular markers also provide an opportunity for new targeted therapies. Beyond single-gene alterations, epigenetic modifications, such as DNA methylation, histone modifications, and noncoding RNA dysregulation, are emerging as important contributors to PitNET pathogenesis and potential therapeutic targets. Multi-omics approaches encompassing genomics, transcriptomics, epigenomics, and proteomics are transforming PitNET classification. In this review, we provide a comprehensive, data-driven update on somatic driver alterations, epigenetic alterations, converging signaling pathways, and the related emerging therapeutic targets in PitNETs, integrating pooled analyses from published cohorts.

Humans↗
PubMed1987

Phenotypes of HeLa S3 variant cell lines resistant to growth inhibition by sodium butyrate.

HeLa cell variants capable of multiplying in the presence of sodium butyrate were used to study the relationship of cell cycle position to human chorionic gonadotropin (hCG) production and regulation of the genes encoding hCG alpha- and beta-subunits. The butyrate-resistant variants exhibit several different stable phenotypes. In wild-type HeLa cells, butyrate arrests cell division and modulates synthesis of alpha- and beta-subunits of glycoprotein hormones by coordinately regulating steady-state levels of their respective mRNAs. Because the variant cell lines replicate, in addition to producing hCG subunits in the presence of butyrate, cell cycle arrest does not seem to be a requirement for expression of glycoprotein hormone genes. Studies of histone modification suggest that neither hyperacetylation of histones H3 and H4 nor dephosphorylation of histones H1 and H2A mediates inhibition of cell replication. In the variants, alpha-subunit and hCG beta levels are independently regulated, as a consequence of independent regulation of alpha- and beta-hCG mRNA levels. Long-term effects of butyrate include derepression of some genes (hCG beta in the variant AO) and repression of others (hCG alpha in variant AO). Moreover, hormone production correlates with the steady-state levels of mRNA for each of the subunits, suggesting that regulation occurs before translation. These findings indicate that the butyrate-resistant variant cell lines are valuable for studies of the molecular mechanisms involved in regulation of expression of ectopic hormones.

Acetylation↗
PubMed2026

Establishment of a Common Marmoset Lineage Carrying a Frameshift Mutation in SETD1A, a Schizophrenia Risk Gene.

Appropriate histone modifications are essential for maintaining functional chromatin structure and gene expression, and dysfunction of their regulators has been linked to a variety of diseases. Among these modifications, trimethylation of lysine 4 on histone H3 (H3K4me3) is a well-characterized epigenetic mark enriched at transcription start sites of actively transcribed genes. H3K4me3 regulates gene transcription by recruiting transcription factors, facilitating chromatin accessibility, and preventing DNA methylation. In mammals, methylation of H3K4 is catalyzed by a family of histone methyltransferases including SET domain containing 1A (SETD1A), which is primarily responsible for genome-wide deposition of H3K4me2/3. Loss-of-function variants in SETD1A, highlighting its critical role in brain development and cognitive function, are strongly associated with schizophrenia (SCZ) and other neurodevelopmental disorders, but the underlying mechanisms remain largely unclear. To better understand the epigenetic and neurobiological consequences of SETD1A dysfunction, non-human primate models can serve as a useful tool because of their close evolutionary relationship to humans and highly developed cognitive abilities. In this study, we established a genetically engineered common marmoset (Callithrix jacchus) lineage carrying a frameshift mutation in SETD1A, which is, to the best of our knowledge, the first non-human primate lineage carrying a mutation in an epigenetic regulatory gene associated with SCZ, and confirmed germline transmission of the mutant allele. In a comparison between fibroblasts derived from one SETD1A mutant and one wild-type marmoset, the mutant showed a lower SETD1A protein level, modest differences in H3K4me3 deposition, and broader differences in gene expression profiles. Although these molecular observations require validation using additional biological replicates, the establishment of this SETD1A mutant marmoset lineage provides a valuable platform for bridging molecular mechanisms with primate neurobiology and for investigating the role of epigenetic regulation in the pathophysiology of neuropsychiatric and neurodevelopmental disorders.

Animals↗
PubMed2025

Advances in tumor subclone formation and mechanisms of growth and invasion.

Tumor subclones refer to distinct cell populations within the same tumor that possess different genetic characteristics. They play a crucial role in understanding tumor heterogeneity, evolution, and therapeutic resistance. The formation of tumor subclones is driven by several key mechanisms, including the inherent genetic instability of tumor cells, which facilitates the accumulation of novel mutations; selective pressures from the tumor microenvironment and therapeutic interventions, which promote the expansion of certain subclones; and epigenetic modifications, such as DNA methylation and histone modifications, which alter gene expression patterns. Major methodologies for studying tumor subclones include single-cell sequencing, liquid biopsy, and spatial transcriptomics, which provide insights into clonal architecture and dynamic evolution. Beyond their direct involvement in tumor growth and invasion, subclones significantly contribute to tumor heterogeneity, immune evasion, and treatment resistance. Thus, an in-depth investigation of tumor subclones not only aids in guiding personalized precision therapy, overcoming drug resistance, and identifying novel therapeutic targets, but also enhances our ability to predict recurrence and metastasis risks while elucidating the mechanisms underlying tumor heterogeneity. The integration of artificial intelligence, big data analytics, and multi-omics technologies is expected to further advance research in tumor subclones, paving the way for novel strategies in cancer diagnosis and treatment. This review aims to provide a comprehensive overview of tumor subclone formation mechanisms, evolutionary models, analytical methods, and clinical implications, offering insights into precision oncology and future translational research.

Humans↗
PubMed1980

Acetylation of histone H4 and its role in chromatin structure and function.

Histone h4 is a highly conserved structural component of the nucleosome subunit of chromatin. The activation of chromatin is accompanied by changes in structure which may be caused by histone modification or by interactions of specific non-histone proteins, or both. Histone H4 can be modified by acetylation and this modification has been correlated with chromosome assembly and with transcription. We have now tested these correlations by studying H4 acetate content as a function of the cell cycle using the naturally synchronous cell cycle in Physarum polycephalum. The results show two clear correlations: (1) tetra-acetylated H4 correlates with transcription; (2) highly acetylated H4 (2 to 4 acetates per molecule) is inversely correlated with H1 phosphorylation and initiation of chromosome condensation in prophase. The results are consistent with turnover of di-acetylated H4 during chromosome assembly in S phase.

Acetylation↗
PubMed1991

Interaction of RNA polymerase II with acetylated nucleosomal core particles.

Chemical acetylation of nucleosomal cores is accompanied by an increase in their efficiency as in vitro transcription templates. Low amounts of acetic anhydride cause preferential modification of the amino-terminal tails of core histones. Modification of these domains, which causes moderate structural effects, is apparently correlated with the observed stimulation of RNA synthesis. In contrast, extensive modification of the globular regions of core histones, which is accompanied by a large structural relaxation of the particle, causes little additional effect on transcription. Acetylation of the amino-terminal domains of histones might stimulate transcription by changing the interaction of the histone tails with components of the transcriptional machinery.

Acetic Anhydrides↗
PubMed2026

Epigenetic modulators in triple-negative breast cancer: epigenetic modifications and future treatment perspectives.

Triple Negative Breast Cancer (TNBC), an aggressive type of Breast Cancer (BC) characterized by the loss of expression of Estrogen Receptor (ER), Progesterone Receptor (PR), and Human Epidermal growth factor Receptor 2 (HER2) protein. TNBC is quite heterogenous in nature with limited available therapeutic options due to the lack of defined molecular targets. Epigenetic abnormalities have been implicated in the onset, progression, immune escape, and resistance to treatment in TNBC. Important epigenetic modulations, include DNA methylation, histone lactylation, histone modifications, and chromatin remodeling. Global hypomethylation contributes to genomic instability, while promoter hypermethylation inhibits tumor suppressor genes, by dysregulating their expression, thereby promoting uncontrolled proliferation, EMT, metastasis, and immune evasion in TNBC. Targeting epigenetic modulators, have the potential to develop novel therapeutic interventions have been developed and being explored. These epidrugs have proven to be effective in preclinical and clinical trials when used in combination with chemotherapy, immunotherapy, or targeted therapy, reducing drug resistance and aberrant proliferation. Despite of the advancements, challenges like target specificity, precise biomarkers and treatment related toxicity are the major hurdles. The review comprehensively summarized the important epigenetic alterations as well as novel treatment strategies with potential clinical applications in TNBC.

Humans↗