The Role of Nuclear Receptor-Binding SET Domain Family Histone Lysine Methyltransferases in Cancer

NSD2 promotes ventricular remodelling mediated by the regulation of H3K36me2

Histone lysine methylation plays an important role in the regulation of ventricular remodelling. NSD2 is involved in many types of tumours through enhancing H3K36me2 expression. However, the role of NSD2 in the regulation of histone lysine methylation during ventricular remodelling remains unclear. In this study, we established cardiac hypertrophy model in C57BL/6 mice by transverse aortic constriction and found that histone lysine methylation participated in ventricular remodelling regulation via the up‐regulation of H3K27me2 and H3K36me2 expression. In addition, we constructed transgenic C57BL/6 mice with conditional knockout of NSD2 (NSD2^−/−) in the myocardium. NSD2^−/− C57BL/6 mice had milder ventricular remodelling and significantly improved cardiac function compared with wild‐type mice, and the expression of H3K36me2 but not H3K27me2 was down‐regulated. In conclusion, NSD2 promotes ventricular remodelling mediated by the regulation of H3K36me2.

Roles of H3K36-specific histone methyltransferases in transcription: antagonizing silencing and safeguarding transcription fidelity

Histone H3K36 methylation is well-known for its role in active transcription. In Saccharomyces cerevisiae, H3K36 methylation is mediated solely by SET2 during transcription elongation. In metazoans, multiple H3K36-specific methyltransferases exist and contribute to distinct biochemical activities and subsequent functions. In this review, we focus on the H3K36-specific histone methyltransferases in metazoans, and discuss their enzymatic activity regulation and their roles in antagonizing Polycomb silencing and safeguarding transcription fidelity.

The role of histone lysine methyltransferase NSD3 in cancer

The growing number of findings demonstrate that nuclear receptor suppressor of variegation, enhancer of zeste, and trithorax domain-containing 3 (NSD3) is amplified and overexpressed in multiple cancer types. Nevertheless, the biological roles of NSD3 in carcinogenesis have not been well understood. In this review, we summarize the current knowledge on the mechanisms underlying NSD3 regulation in different cancers. In addition, NSD3 may serve as a potential druggable target for selective cancer therapy in the future.

High-throughput screening with nucleosome substrate identifies small-molecule inhibitors of the human histone lysine methyltransferase NSD2

The histone lysine methyltransferase nuclear receptor-binding SET domain protein 2 (NSD2, also known as WHSC1/MMSET) is an epigenetic modifier and is thought to play a driving role in oncogenesis. Both NSD2 overexpression and point mutations that increase its catalytic activity are associated with several human cancers. Although NSD2 is an attractive therapeutic target, no potent, selective, and bioactive small molecule inhibitors of NSD2 have been reported to date, possibly due to the challenges of developing high-throughput assays for NSD2. Here, to establish a platform for the discovery and development of selective NSD2 inhibitors, we optimized and implemented multiple assays. We performed quantitative high-throughput screening with full-length WT NSD2 and a nucleosome substrate against a diverse collection of bioactive small molecules comprising 16,251 compounds. We further interrogated 174 inhibitory compounds identified in the primary screen with orthogonal and counter assays and with activity assays based on the clinically relevant NSD2 variants E1099K and T1150A. We selected five confirmed inhibitors for follow-up, which included a radiolabeled validation assay, surface plasmon resonance studies, methyltransferase profiling, and histone methylation in cells. We found that all five NSD2 inhibitors bind the catalytic SET domain and one exhibited apparent activity in cells, validating the workflow and providing a template for identifying selective NSD2 inhibitors. In summary, we have established a robust discovery pipeline for identifying potent NSD2 inhibitors from small-molecule libraries.

Chemical and Biochemical Perspectives of Protein Lysine Methylation

Protein lysine methylation is a distinct posttranslational modification that causes minimal changes in the size and electrostatic status of lysine residues. Lysine methylation plays essential roles in regulating fates and functions of target proteins in an epigenetic manner. As a result, substrates and degrees (free versus mono/di/tri) of protein lysine methylation are orchestrated within cells by balanced activities of protein lysine methyltransferases (PKMTs) and demethylases (KDMs). Their dysregulation is often associated with neurological disorders, developmental abnormalities, or cancer. Methyllysine-containing proteins can be recognized by downstream effector proteins, which contain methyllysine reader domains, to relay their biological functions. While numerous efforts have been made to annotate biological roles of protein lysine methylation, limited work has been done to uncover mechanisms associated with this modification at a molecular or atomic level. Given distinct biophysical and biochemical properties of methyllysine, this review will focus on chemical and biochemical aspects in addition, recognition, and removal of this posttranslational mark. Chemical and biophysical methods to profile PKMT substrates will be discussed along with classification of PKMT inhibitors for accurate perturbation of methyltransferase activities. Semisynthesis of methyllysine-containing proteins will also be covered given the critical need for these reagents to unambiguously define functional roles of protein lysine methylation.

Relationship between NSD2 and tumors

Nuclear receptor binding SET domain-protein 2 (NSD2), also known as MMSET or WHSC1, is a member of the NSD family. Methylation of histone as an important regulatory mechanism in epigenetics plays an important role in transcriptional regulation and chromatin remodeling. The overexpression of NSD2, caused by t(4; 14) (p16; q23) translocation, is closely related to the prognosis of patients with multiple myeloma. In addition, high expression of NSD2 can be detected in many other malignant tumors. NSD2 catalyzes the methylation of the lysine sites of histone, and promotes the initiation and progression of tumors by participating in the interaction among multiple proteins or the regulation of target genes. NSD2 and related signal molecules are expected to be the targets for treatment of various related tumors. Elucidating the mechanism of NSD2 may promote the development of targeted drugs and provide new solutions for the treatment of various NSD2-related tumors.

Epigenetic regulatory mutations and epigenetic therapy for multiple myeloma

PURPOSE OF REVIEW

Next generation sequencing and large-scale analysis of patient specimens has created a more complete picture of multiple myeloma (MM) revealing that epigenetic deregulation is a prominent factor in MM pathogenesis.

RECENT FINDINGS

Over half of MM patients have mutations in genes encoding epigenetic modifier enzymes. The DNA methylation profile of MM is related to the stage of the disease and certain classes of mutations in epigenetic modifiers are more prevalent upon disease relapse, suggesting a role in disease progression. Many small molecules targeting regulators of epigenetic machinery have been developed and clinical trials are underway for some of these in MM.

SUMMARY

Recent findings suggest that epigenetic targeting drugs could be an important strategy to cure MM. Combining these agents along with other strategies to affect the MM cell such as immunomodulatory drugs and proteasome inhibitors may enhance efficacy of combination regimens in MM.