Dataset Information

Viral mutations enhance the Max binding properties of the vMyc b-HLH-LZ domain.

ABSTRACT: Interaction with Max via the helix-loop-helix/leucine zipper (HLH-LZ) domain is essential for Myc to function as a transcription factor. Myc is commonly upregulated in tumours, however, its activity can also be potentiated by virally derived mutations. vMyc, derived from the virus, MC29 gag-Myc, differs from its cellular counterpart by five amino acids. The N-terminal mutation stabilizes the protein, however, the significance of the other mutations is not known. We now show that vMyc can sustain longer deletions in the LZ domain than cMyc before complete loss in transforming activity, implicating the viral mutations in contributing to Myc:Max complex formation. We confirmed this both in vitro and in vivo, with loss of Max binding correlating with a loss in the biological activity of Myc. A specific viral mutation, isoleucine383>leucine (I383>L) in helix 2 of the HLH domain, extends the LZ domain from four to five heptad repeats. Significantly, introduction of I383>L into a Myc mutant that is defective for Max binding substantially restored its ability to complex with Max in vitro and in vivo. We therefore propose that this virally derived mutation is functional by significantly contributing to establishing a more hydrophobic interface between the LZs of Myc and Max.

SUBMITTER: Crouch DH

PROVIDER: S-EPMC1216337 | biostudies-literature | 2005

REPOSITORIES: biostudies-literature

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Viral mutations enhance the Max binding properties of the vMyc b-HLH-LZ domain.

Crouch D H DH Fisher F F La Rocca S A SA Goding C R CR Gillespie D A F DA

Nucleic acids research 20050915 16

Interaction with Max via the helix-loop-helix/leucine zipper (HLH-LZ) domain is essential for Myc to function as a transcription factor. Myc is commonly upregulated in tumours, however, its activity can also be potentiated by virally derived mutations. vMyc, derived from the virus, MC29 gag-Myc, differs from its cellular counterpart by five amino acids. The N-terminal mutation stabilizes the protein, however, the significance of the other mutations is not known. We now show that vMyc can sustain ...[more]

PMID: 16166655

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Project description:Most adult patients have a D816V mutation in phosphotransferase domain (PTD), we have described that half of the children carry mutations in extracellular domain (ECD). KIT-ECD versus IT-PTD-mutants were introduced into rodent Ba/F3, EML, Rat2 and human TF1 cells to investigate their biological effect. ECD- and PTD-mutants also displayed distinct whole-genome transcriptional profiles in EML cells. We observed differences in their signaling properties: they both activated STAT pathways, whereas AKT pathway was only activated by ECD-mutants. Consistently, AKT inhibitor suppressed ECD-mutant-dependent proliferation, clonogenicity and erythroid differentiation. Expression of myristoylated AKT restored erythroid differentiation in EMLPTD cells, suggesting the differential role of AKT in those mutants. Overall, our study implied different pathogenesis of pediatric versus adult mastocytosis, which might explain their diverse phenotypes. Each EML cell line (Del417-419insY mutant and D816V mutant) was cultured with or without 250 ng/mL SCF for 48h. Gene expression profile analysis was performed using whole-genome microarrays. RNA expression profiling of cell lines was done with Affymetrix M430 2.0 mouse oligonucleotide microarrays containing 45.101 probe sets, representing 21.408 transcripts and variants including 17.482 well-characterized mouse genes. Preparation of cRNA, hybridizations, washes, detection and quantification were done as recommended by the supplier. For each sample, synthesis of the first-strand cDNA was done from 3 μg total RNA by T7-oligo(dT) priming, followed by second-strand cDNA synthesis. After purification, in vitro transcription associated with amplification generated cRNA-containing biotinylated pseudouridine. Biotinylated cRNA was purified, quantified and chemically fragmented (95°C for 35 min), then hybridized to microarrays in 200 μL hybridization buffer at 45°C for 16 h. Automated washes and staining with streptavidin-phycoerythrin were done as recommended. Signal amplification was done by biotinylated antistreptavidin antibody with goat-IgG blocking antibody. Scanning was done with Affymetrix GeneArray scanner and quantification with Affymetrix GCOS software.

Project description:Background:Genomic studies have revealed that multiple genes are mutated at varying frequency in endometrial cancer (EC); however, the relevance of many of these mutations is poorly understood. An EC-specific recurrent mutation in the MAX transcription factor p.His28Arg was recently discovered. We sought to assess the functional consequences of this hotspot mutation and determine its association with cancer-relevant phenotypes. Methods:MAX was sequenced in 509 endometrioid ECs, and associations between mutation status and clinicopathologic features were assessed. EC cell lines stably expressing MAXH28R were established and used for functional experiments. DNA binding was examined using electrophoretic mobility shift assays and chromatin immunoprecipitation. Transcriptional profiling was performed with microarrays. Murine flank (six to 11 mice per group) and intraperitoneal tumor models were used for in vivo studies. Vascularity of xenografts was assessed by MECA-32 immunohistochemistry. The paracrine pro-angiogenic nature of MAXH28R-expressing EC cells was tested using microfluidic HUVEC sprouting assays and VEGFA enzyme-linked immunosorbent assays. All statistical tests were two-sided. Results:Twenty-two of 509 tumors harbored mutations in MAX, including 12 tumors with the p.His28Arg mutation. Patients with a MAX mutation had statistically significantly reduced recurrence-free survival (hazard ratio = 4.00, 95% confidence interval = 1.15 to 13.91, P = .03). MAXH28R increased affinity for canonical E-box sequences, and MAXH28R-expressing EC cells dramatically altered transcriptional profiles. MAXH28R-derived xenografts statistically significantly increased vascular area compared with MAXWT and empty vector tumors (P = .003 and P = .008, respectively). MAXH28R-expressing EC cells secreted nearly double the levels of VEGFA compared with MAXWT cells (P = .03, .005, and .005 at 24, 48, and 72 hours, respectively), and conditioned media from MAXH28R cells increased sprouting when applied to HUVECs. Conclusion:These data highlight the importance of MAX mutations in EC and point to increased vascularity as one mechanism contributing to clinical aggressiveness of EC.

Dataset Information

Viral mutations enhance the Max binding properties of the vMyc b-HLH-LZ domain.

Publications

Viral mutations enhance the Max binding properties of the vMyc b-HLH-LZ domain.

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