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| MYCL | |
|---|---|
| Name | MYCL |
| HGNCSymbol | MYCL |
| EntrezGene | 4613 |
| OMIM | 164870 |
| RefSeq | NM_002457 |
| UniProt | P12532 |
| Chromosomal location | 1p34.2 |
MYCL
MYCL is a human proto-oncogene encoding a member of the MYC family of basic helix-loop-helix leucine zipper transcription factors implicated in cell proliferation, differentiation, and oncogenesis. It is related to MYC (gene), MYCN, and functions in transcriptional regulation by heterodimerizing with partners to bind E-box elements in regulatory regions of target genes. MYCL has been studied in the context of diverse malignancies, developmental biology, and transcriptional networks involving TP53, RB1, and chromatin modifiers such as EP300.
MYCL is one of three canonical MYC family members alongside MYC (gene) and MYCN, first identified through studies of avian myelocytomatosis and later mapped to human chromosome 1p34.2. It encodes a protein of the basic helix-loop-helix leucine zipper (bHLH-LZ) class that regulates transcription by forming heterodimers with partner proteins. MYCL expression is tissue-restricted compared with MYC (gene) and MYCN, with notable roles in pulmonary epithelium and hematopoietic lineages; dysregulation is associated with tumors such as small cell lung carcinoma, neuroendocrine tumors, and subsets of lymphoma.
The MYCL locus spans multiple exons and produces transcripts subject to alternative promoter usage and splicing similar to patterns seen for MYC (gene) family members. The encoded protein contains an N-terminal transactivation domain with conserved Myc boxes (MBI, MBII) that mediate interactions with coactivators and E3 ligases, and a C-terminal bHLH-LZ domain responsible for DNA binding and dimerization with partners like MAX (protein). Structural studies have exploited comparisons to crystal structures of bHLH-LZ proteins such as USF1 and Mad1 to infer conformational features. Post-translational modifications mapped to MYCL include phosphorylation sites recognized by kinases such as GSK3B and ubiquitination signals processed by complexes containing FBXW7.
MYCL acts primarily as a sequence-specific transcription factor that binds E-box motifs (CACGTG) in promoters and enhancers to regulate genes controlling ribosome biogenesis, metabolism, and cell cycle progression. It exerts both activation and repression through recruitment of chromatin modifiers including TRRAP, EP300, and components of the SWI/SNF complex, and competes with MXD family repressors like MXD1 for shared partners. MYCL-mediated transcriptional programs overlap with those of MYC (gene) and MYCN but show distinct target preferences linked to cell-type specific cofactors such as ASCL1 in neuroendocrine lineages. Mechanistically, MYCL integrates signals from pathways involving PI3KCA, AKT1, and MAPK1 to tune anabolic and proliferative responses.
MYCL expression and activity are controlled at multiple levels: transcriptional regulation by factors including E2F1, NOTCH1, and HIF1A; post-transcriptional modulation via RNA-binding proteins like IGF2BP1 and microRNAs such as members of the let-7 family; and post-translational control by phosphorylation, ubiquitination, and proteasomal degradation mediated by enzymes including GSK3B and ubiquitin ligases like FBXW7. Genomic alterations such as focal amplification of the MYCL locus, promoter hypomethylation, or enhancer hijacking by TERT promoter rearrangements have been observed in tumors. Negative regulation involves tumor suppressors such as TP53 and RB1, which indirectly restrict MYCL-driven programs.
Aberrant MYCL activity contributes to oncogenesis in several human cancers; focal amplification or overexpression is notable in subsets of small cell lung carcinoma, pulmonary neuroendocrine tumors, and some hematologic malignancies including diffuse large B-cell lymphoma. MYCL status can influence prognosis, therapeutic responsiveness to inhibitors targeting transcriptional dependencies (for example, agents disrupting CDK9 or bromodomain proteins like BRD4), and sensitivity to metabolic interventions affecting pathways downstream of MYC family proteins. MYCL alterations occasionally co-occur with mutations in RB1, TP53, or activation of PIK3CA pathway components, informing combination therapy strategies. Clinical biomarker efforts evaluate MYCL copy number, mRNA expression, and protein levels using techniques established by The Cancer Genome Atlas and clinical laboratories.
MYCL forms heterodimers with classical partners such as MAX (protein), and competes with MXD family members like MXD1 and MNT for binding. It recruits coactivators and chromatin regulators including TRRAP, EP300, and members of the CBP complex, and engages ubiquitin pathway components like FBXW7 and SKP2 for turnover. Interactions with transcription factors such as ASCL1, NEUROD1, and E2F1 shape lineage-specific programs, while cross-talk with signaling mediators including AKT1, GSK3B, and MAPK1 integrates extracellular cues. MYCL-dependent complexes have been profiled together with proteomic platforms used by groups led in part by investigators associated with Broad Institute and European Bioinformatics Institute.
Experimental studies use genetically engineered mouse models, such as conditional transgenic alleles and knockout mice, to elucidate MYCL function in development and tumorigenesis, paralleling models for MYC (gene) and MYCN. Xenograft studies with cell lines derived from small cell lung carcinoma and patient-derived xenografts assess MYCL-driven oncogenicity and therapeutic vulnerabilities. CRISPR-based screens in cell panels from resources like Cancer Cell Line Encyclopedia have identified synthetic lethal interactions involving genes such as CDK1 and PSMC3. Comparative studies in zebrafish and Drosophila leverage conserved bHLH factors to dissect developmental roles and regulatory networks mapped in resources like GENCODE.
Category:Human genes