Peptide inhibition of the SETD6 methyltransferase catalytic activity. Oncotarget. 2017;9:4875-4885. [PMID: 29435148 PMCID: PMC5797019 DOI: 10.18632/oncotarget.23591]

Marine algae-derived oligosaccharide via protein crotonylation of key targeting for management of type 2 diabetes mellitus in the elderly

Global aging is a tendency of the world, as is the increasing prevalence of diabetes, and the two are closely linked. In our early research, Enteromorpha prolifera oligosaccharide (EPO) possesses the excellent ability of anti-oxidative, anti-inflammatory, and anti-diabetic. We aim to further explore the deeper mechanism of how EPO delays aging and regulates glycometabolism. EPO effectively impacts crotonylation procession to enhance glucose metabolism and reduce cell senescence in aging diabetic rats. Crotonylation modification of XPO1 influences the expression of critical genes, including p53, CDK1, and CCNB1, which affect cell cycle regulation and aging. Additionally, EPO improves glucose metabolism by inhibiting the crotonylation modification of HSPA8-K126 and activating the AKT pathway. EPO promotes crotonylation of histones in intestinal cells, influencing the aging process by increasing the butyric acid-producing bacteria Ruminococcaceae. The observed enhancement in pyrimidine metabolism underscores EPO's potential role in regulating intestinal health, presenting a promising avenue for delaying aging. In summary, our findings affirm EPO as a naturally bioactive ingredient with significant potential for anti-aging and antidiabetic interventions.

Transdermal Properties of Cell-Penetrating Peptides: Applications and Skin Penetration Mechanisms

Cell-penetrating peptides (CPPs) consist of 5-30 amino acids with intracellular transduction abilities and diverse physicochemical properties, origins, and sequences. Although recent developments in bioinformatics have facilitated the prediction of CPP candidates with the potential for transduction into cells, the mechanisms by which CPPs penetrate cells and various tissues have not yet been elucidated at the molecular interaction level. Recently, the skin-penetrating ability of CPPs has gained wide attention and emerged as a simple and effective strategy for the delivery of macromolecules into the skin. Studies on the skin structure have suggested that the penetration potential of CPPs is based on the molecular interactions and characteristics of the lipid lamellar structure between corneocytes in the stratum corneum. This review provides a brief overview of the general properties, transduction mechanisms, applications, and safety issues of CPPs, focusing on CPPs with transdermal properties, that are currently being used to develop therapeutics and cosmetics.

Methylation of the transcription factor E2F1 by SETD6 regulates SETD6 expression via a positive feedback mechanism

The protein lysine methyltransferase SET domain-containing protein 6 (SETD6) has been shown to influence different cellular activities and to be critically involved in the regulation of diverse developmental and pathological processes. However, the upstream signals that regulate the mRNA expression of SETD6 are not known. Bioinformatic analysis revealed that the SETD6 promoter has a binding site for the transcription factor E2F1. Using various experimental approaches, we show that E2F1 binds to the SETD6 promoter and regulates SETD6 mRNA expression. Our further observation that this phenomenon is SETD6 dependent suggested that SETD6 and E2F1 are linked. We next demonstrate that SETD6 monomethylates E2F1 specifically at K117 in vitro and in cells. Finally, we show that E2F1 methylation at K117 positively regulates the expression level of SETD6 mRNA. Depletion of SETD6 or overexpression of E2F1 K117R mutant, which cannot be methylated by SETD6, reverses the effect. Taken together, our data provide evidence for a positive feedback mechanism, which regulates the expression of SETD6 by E2F1 in a SETD6 methylation-dependent manner, and highlight the importance of protein lysine methyltransferases and lysine methylation signaling in the regulation of gene transcription.

TWIST1 methylation by SETD6 selectively antagonizes LINC-PINT expression in glioma

Gliomas are one of the most common and lethal brain tumors among adults. One process that contributes to glioma progression and recurrence is the epithelial to mesenchymal transition (EMT). EMT is regulated by a set of defined transcription factors which tightly regulate this process, among them is the basic helix-loop-helix family member, TWIST1. Here we show that TWIST1 is methylated on lysine-33 at chromatin by SETD6, a methyltransferase with expression levels correlating with poor survival in glioma patients. RNA-seq analysis in U251 glioma cells suggested that both SETD6 and TWIST1 regulate cell adhesion and migration processes. We further show that TWIST1 methylation attenuates the expression of the long-non-coding RNA, LINC-PINT, thereby promoting EMT in glioma. Mechanistically, TWIST1 methylation represses the transcription of LINC-PINT by increasing the occupancy of EZH2 and the catalysis of the repressive H3K27me3 mark at the LINC-PINT locus. Under un-methylated conditions, TWIST1 dissociates from the LINC-PINT locus, allowing the expression of LINC-PINT which leads to increased cell adhesion and decreased cell migration. Together, our findings unravel a new mechanistic dimension for selective expression of LINC-PINT mediated by TWIST1 methylation.

Protein Delivery to Cytosol by Cell-Penetrating Peptide Bearing Tandem Repeat Penetration-Accelerating Sequence

Pas2r12 is comprised of a repeat of the penetration-accelerating sequence (Pas) (Pas2: FFLIG-FFLIG) and D-form dodeca-arginine (r12), a cell-penetrating peptide. Pas2r12 significantly enhances cytosolic delivery of cargo proteins, including enhanced green fluorescent protein and immunoglobulin G. Simply incubating Pas2r12 with cargo leads to their cytosolic tranlsocation. Cytosolic delivery of cargo by Pas2r12 involves caveolae-mediated endocytosis. In this chapter, we describe methods of cytosolic delivery of cargo using Pas2r12 and provide methods for investigating the cellular uptake pathway of cargo by Pas2r12.

Exome hits demystified: The next frontier

Severe mental illnesses such as schizophrenia and bipolar disorder have complex inheritance patterns, involving both common and rare variants. Whole exome sequencing is a promising approach to find out the rare genetic variants. We had previously reported several rare variants in multiplex families with severe mental illnesses. The current article tries to summarise the biological processes and pattern of expression of genes harbouring the aforementioned variants, linking them to known clinical manifestations through a methodical narrative review. Of the 28 genes considered for this review from 7 families with multiple affected individuals, 6 genes are implicated in various neuropsychiatric manifestations including some variations in the brain morphology assessed by magnetic resonance imaging. Another 15 genes, though associated with neuropsychiatric manifestations, did not have established brain morphological changes whereas the remaining 7 genes did not have any previously recorded neuropsychiatric manifestations at all. Wnt/b-catenin signaling pathway was associated with 6 of these genes and PI3K/AKT, calcium signaling, ERK, RhoA and notch signaling pathways had at least 2 gene associations. We present a comprehensive review of biological and clinical knowledge about the genes previously reported in multiplex families with severe mental illness. A 'disease in dish approach' can be helpful to further explore the fundamental mechanisms.

PAK4 methylation by the methyltransferase SETD6 attenuates cell adhesion

P21-activated kinase 4 (PAK4), a member of serine/threonine kinases family is over-expressed in numerous cancer tumors and is associated with oncogenic cell proliferation, migration and invasion. Our recent work demonstrated that the SET-domain containing protein 6 (SETD6) interacts with and methylates PAK4 at chromatin in mammalian cells, leading to activation of the Wnt/β-catenin signaling pathway. In our current work, we identified lysine 473 (K473) on PAK4 as the primary methylation site by SETD6. Methylation of PAK4 at K473 activates β-catenin transcriptional activity and inhibits cell adhesion. Specific methylation of PAK4 at K473 also attenuates paxillin localization to focal adhesions leading to overall reduction in adhesion-related features, such as filopodia and actin structures. The altered adhesion of the PAK4 wild-type cells is accompanied with a decrease in the migrative and invasive characteristics of the cells. Taken together, our results suggest that methylation of PAK4 at K473 plays a vital role in the regulation of cell adhesion and migration.

Colon cancer stemness as a reversible epigenetic state: Implications for anticancer therapies

The recent discovery of cancer cell plasticity, i.e. their ability to reprogram into cancer stem cells (CSCs) either naturally or under chemotherapy and/or radiotherapy, has changed, once again, the way we consider cancer treatment. If cancer stemness is a reversible epigenetic state rather than a genetic identity, opportunities will arise for therapeutic strategies that remodel epigenetic landscapes of CSCs. However, the systematic use of DNA methyltransferase and histone deacetylase inhibitors, alone or in combination, in advanced solid tumors including colorectal cancers, regardless of their molecular subtypes, does not seem to be the best strategy. In this review, we first summarize the knowledge researchers have gathered on the epigenetic signatures of CSCs with the difficulty of isolating rare populations of cells. We raise questions about the relevant use of currently available epigenetic inhibitors (epidrugs) while the expression of numerous cancer stem cell markers are often repressed by epigenetic mechanisms. These markers include the three cluster of differentiation CD133, CD44 and CD166 that have been extensively used for the isolation of colon CSCs.and . Finally, we describe current treatment strategies using epidrugs, and we hypothesize that, using correlation tools comparing associations of relevant CSC markers with chromatin modifier expression, we could identify better candidates for epienzyme targeting.

Lysine methylation signaling of non-histone proteins in the nucleus

Lysine methylation, catalyzed by protein lysine methyltransferases (PKMTs), is a central post-translational modification regulating many signaling pathways. It has direct and indirect effects on chromatin structure and transcription. Accumulating evidence suggests that dysregulation of PKMT activity has a fundamental impact on the development of many pathologies. While most of these works involve in-depth analysis of methylation events in the context of histones, in recent years, it has become evident that methylation of non-histone proteins also plays a pivotal role in cell processes. This review highlights the importance of non-histone methylation, with focus on methylation events taking place in the nucleus. Known experimental platforms which were developed to identify new methylation events, as well as examples of specific lysine methylation signaling events which regulate key transcription factors, are presented. In addition, the role of these methylation events in normal and disease states is emphasized.

Cell-penetrating peptide: a means of breaking through the physiological barriers of different tissues and organs

The selective infiltration of cell membranes and tissue barriers often blocks the entry of most active molecules. This natural defense mechanism prevents the invasion of exogenous substances and limits the therapeutic value of most available molecules. Therefore, it is particularly important to find appropriate ways of membrane translocation and therapeutic agent delivery to its target site. Cell penetrating peptides (CPPs) are a group of short peptides harnessed in this condition, possessing a significant capacity for membrane transduction and could be exploited to transfer various biologically active cargoes into the cells. Since their discovery, CPPs have been employed for delivery of a wide variety of therapeutic molecules to treat various disorders including cranial nerve involvement, ocular inflammation, myocardial ischemia, dermatosis and cancer. The promising results of CPPs-derived therapeutics in various tumor models demonstrated a potential and worthwhile scope of CPPs in chemotherapy. This review describes the detailed description of CPPs and CPPs-assisted molecular delivery against various tissues and organs disorders. An emphasis is focused on summarizing the novel insights and achievements of CPPs in surmounting the natural membrane barriers during the last 5 years.

Oligoarginine-Bearing Tandem Repeat Penetration-Accelerating Sequence Delivers Protein to Cytosol via Caveolae-Mediated Endocytosis

To facilitate the cytosolic delivery of larger molecules such as proteins, we developed a new cell-penetrating peptide sequence, named Pas2r12, consisting of a repeated Pas sequence (FFLIG-FFLIG) and d-dodeca-arginine (r12). This peptide significantly enhanced the cellular uptake and cytosolic release of enhanced green fluorescent protein and immunoglobulin G as cargos. We found that simply mixing Pas2r12 with cargos could generate cytosolic introducible forms. The cytosolic delivery of cargos by Pas2r12 was found to be an energy-requiring process, to rely on actin polymerization, and to be suppressed by caveolae-mediated endocytosis inhibitors (genistein and methyl-β-cyclodextrin) and small interfering RNA against caveolin-1. These results suggest that Pas2r12 enhances membrane penetration of cargos without the need for cross-linking and that caveolae-mediated endocytosis may be the route by which cytosolic delivery is enhanced.

Oligomerization and Auto-methylation of the Human Lysine Methyltransferase SETD6

Signaling via lysine methylation by protein lysine methyltransferases (PKMTs), has been linked to diverse biological and disease processes. The mono-methyltransferase SETD6 (SET-domain-containing protein 6) is a member of the PKMT family and was previously shown to regulate essential cellular processes such as the NF-κB, WNT and the oxidative stress pathways. However, on the biochemical level, little is known about the enzymatic mode of action of SETD6. Here we provide evidence that SETD6 forms high-molecular-weight structures. Specifically, we demonstrate that SETD6 monomeric, dimeric and trimeric forms are stabilized by the methyl donor, S-adenosyl-l-methionine. We then show that SETD6 has auto-methylation activity at K39 and K179, which serves as the major auto-methylation sites with a moderate auto-methylation activity toward K372. A point mutation at K179 but not at K39 and K372, located at the SET domain of SETD6, impaired SETD6 ability to form a trimer, strongly implying a link between the auto-methylation and the oligomerization state. Finally, by radioactive in vitro methylation experiments and biochemical kinetics analysis, we show that the auto-methylation at K39 and K179 increases the catalytic rate of SETD6. Collectively, our data support a model by which SETD6 auto-methylation and self-interaction positively regulate its enzymatic activity in vitro and may suggest that other PKMTs are regulated in the same manner.