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| Menin | |
|---|---|
| Name | Menin |
| Uniprot | P46013 |
| Gene loc | 11q13 |
| Length | 610 aa |
| Organism | Homo sapiens |
Menin
Menin is a 610–amino acid nuclear protein encoded by the human MEN1 gene on chromosome 11q13 that functions as a multifaceted regulator of transcription, chromatin architecture, and cell proliferation. Identified through genetic linkage in familial tumor syndromes, menin interacts with numerous transcription factors and epigenetic complexes to influence cell fate in tissues predisposed to endocrine neoplasia. Studies in cell lines, model organisms, and clinical cohorts have delineated menin’s contributions to tumor suppression, developmental regulation, and genome maintenance.
Menin was discovered through mapping studies in familial tumor predisposition pedigrees associated with parathyroid and pituitary tumors and pancreatic neuroendocrine tumors linked to Multiple Endocrine Neoplasia Type 1 (MEN1). The protein localizes predominantly to the nucleus and engages with transcriptional regulators such as JunD, NF-κB, MLL complex components, and chromatin modifiers including HDAC1 and KMT2A. Structural biology and biochemical assays have shown that menin forms interfaces with proteins implicated in transcriptional elongation, RNA processing, and DNA damage response, situating it at the convergence of pathways governed by factors like p53, BRCA1, and ATM.
Menin lacks classical enzymatic domains but contains conserved surfaces that mediate protein–protein interactions. X-ray crystallography and cryo-EM of menin bound to peptides from partners such as JUND and MLL1 revealed an elongated fold with deep binding pockets that accommodate transcriptional regulators. Menin associates with the trithorax-like KMT2A/MLL methyltransferase complex and thereby influences histone H3 lysine 4 methylation, connecting menin to epigenetic marks deposited by complexes that include WDR5, RBBP5, and ASH2L. Menin also binds components of the RNA polymerase II machinery, linking it to factors such as TFIID subunits and MED1 within mediator assemblies.
Functionally, menin acts as a context-dependent scaffold: in pancreatic islets it restricts proliferation by repressing targets via interaction with FOXA2 and PAX6, whereas in hematopoietic contexts it can cooperate with oncogenic fusions like MLL-AF4 to sustain leukemogenic programs. Menin participates in DNA damage signaling through contacts with CHEK1 and RAD51, contributing to genomic stability. Its nuclear localization signals enable menin to modulate nucleosome organization alongside chromatin remodelers such as SWI/SNF subunits.
Germline inactivating variants in MEN1 produce haploinsufficiency or dominant-negative effects that disrupt menin’s interactions with a broad network of transcription factors and epigenetic regulators. Menin binds to homeodomain proteins like PAX6 and ISL1, basic leucine zipper proteins such as JunD and c-Jun, and forkhead factors exemplified by FOXA2. Through the MLL complex, menin cooperates with histone methyltransferases including KMT2A to regulate expression of cyclin-dependent kinase inhibitors like CDKN1B (p27Kip1) and CDKN2C (p18INK4c). Menin also interfaces with nuclear receptors such as Estrogen receptor alpha and VDR, influencing ligand-dependent transcriptional programs.
Post-translational modifications of menin—phosphorylation by kinases such as PKA and ubiquitination mediated by E3 ligases including UBC-containing complexes—modulate its stability and partner selection. Synthetic lethal screens and proteomic maps have connected menin to pathways involving mTOR, PI3K, and MAPK signaling through intermediary transcriptional networks.
Loss-of-function germline variants in MEN1 cause MEN1 syndrome, characterized by tumors of the parathyroid glands, pancreatic islets, and pituitary gland, with variable penetrance and age-dependent expressivity. Somatic second-hit events, including loss of heterozygosity at 11q13, promoter methylation, or truncating mutations, result in biallelic inactivation in neoplastic lesions from patients described in cohorts from referral centers such as NIH and national registries. Tumor suppressor activity of menin is underscored by mouse models bearing Men1 heterozygosity that develop parathyroid and pancreatic endocrine tumors mirroring human phenotype.
Beyond MEN1, altered menin function is implicated in sporadic endocrine neoplasms and in the pathogenesis of leukemias bearing MLL translocations, where menin is co-opted to maintain aberrant HOX gene expression programs mediated by partners like HOXA9 and MEIS1. Clinical manifestations of MEN1 include hypercalcemia from hyperparathyroidism, hypoglycemia or gastrinoma-related acid hypersecretion from pancreatic tumors, and pituitary hormone excess syndromes implicating PRL and GH secreting adenomas.
Genetic testing for pathogenic variants in MEN1 is recommended for at-risk kindreds and individuals with MEN1-spectrum tumors, with molecular diagnostics performed by clinical laboratories accredited by agencies such as ACMG standards. Surveillance guidelines from endocrine societies including ENDO and national specialty groups recommend periodic biochemical screening and imaging modalities like MRI for pituitary, neck ultrasound for parathyroids, and cross-sectional imaging (CT/MRI) or somatostatin receptor imaging using tracers evaluated in trials at centers such as Mayo Clinic.
Therapeutic strategies targeting menin interactions have emerged: small-molecule menin inhibitors that disrupt the menin–MLL interface, developed by academic–industry consortia, show preclinical efficacy against MLL-rearranged leukemia and pancreatic neuroendocrine tumor models. Surgical resection remains mainstay for localized parathyroid and pancreatic lesions, with adjuvant approaches using somatostatin analogs (e.g., octreotide), targeted kinase inhibitors (e.g., everolimus targeting mTOR), and peptide receptor radionuclide therapy informed by expression of SSTR2.
MEN1 mapping emerged from linkage studies in the 1980s and cloning of the MEN1 gene in 1997, by consortia combining geneticists, endocrinologists, and molecular biologists. Seminal work linking menin to transcriptional complexes and chromatin modifiers came from structural biology laboratories and chromatin research groups at institutions including Harvard Medical School, University of Cambridge, and University of Helsinki. Subsequent translational efforts have spanned clinical genetics programs, basic research centers, and pharmaceutical partnerships to translate menin biology into diagnostic assays and targeted therapeutics.
Category:Human proteinsCategory:Tumour suppressors