Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P05412 (c-Jun)
 11,453 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the Jun family of proteins (c-Jun, JunB, and JunD) in oncogenesis has been extensively studied, but the distinct biological roles of each Jun protein is not known. For example, whereas c-Jun can transform primary cells in cooperation with an activated ras oncogene, JunD antagonizes ras-mediated transformation. We have discovered that two isoforms of the JunD transcription factor are ubiquitously expressed, resulting from use of an alternative translation start codon within the JunD mRNA. Here we report the first characterized functional difference between these JunD isoforms; only the full-length isoform of JunD binds to the Menin tumor suppressor protein. Furthermore, Menin suppresses transcriptional activity of the full-length but not the truncated isoform of JunD, which identifies the full-length JunD isoform as a functional target of Menin.
 ...
PMID:Differential binding of the Menin tumor suppressor protein to JunD isoforms. 1122 82

Menin, a nuclear protein encoded by the tumor suppressor gene MEN1, interacts with the AP-1 transcription factor JunD and inhibits its transcriptional activity. In addition, overexpression of Menin counteracts Ras-induced tumorigenesis. We show that Menin inhibits ERK-dependent phosphorylation and activation of both JunD and the Ets-domain transcription factor Elk-1. We also show that Menin represses the inducible activity of the c-fos promoter. Furthermore, Menin expression inhibits Jun N-terminal kinase (JNK)-mediated phosphorylation of both JunD and c-Jun. Kinase assays show that Menin overexpression does not interfere with activation of either ERK2 or JNK1, suggesting that Menin acts at a level downstream of MAPK activation. An N-terminal deletion mutant of Menin that cannot inhibit JunD phosphorylation by JNK, can still repress JunD phosphorylation by ERK2, suggesting that Menin interferes with ERK and JNK pathways through two distinct inhibitory mechanisms. Taken together, our data suggest that Menin uncouples ERK and JNK activation from phosphorylation of their nuclear targets Elk-1, JunD and c-Jun, hence inhibiting accumulation of active Fos/Jun heterodimers. This study provides new molecular insights into the tumor suppressor function of Menin and suggests a mechanism by which Menin may interfere with Ras-dependent cell transformation and oncogenesis.
 ...
PMID:Menin uncouples Elk-1, JunD and c-Jun phosphorylation from MAP kinase activation. 1222 47

The translation product of the MEN1 gene, menin, has been reported to suppress JunD-mediated activator protein-1 (AP-1) transactivation and inhibit Ras-mediated tumor formation, but its molecular mechanisms and physiologic significance have been poorly elucidated. To better understand the function of menin as a tumor suppressor, we examined the effect of menin on physiologically induced AP-1 activity. Overexpression of menin strongly suppressed insulin-induced AP-1 activity in CHO-IR cells, which express high levels of insulin receptor. We found that menin suppressed c-Fos induction at the transcriptional level, although that cannot explain the entire mechanism of AP-1 suppression by menin. Menin did not alter the expression levels of AP-1 proteins except c-Fos, phosphorylation of c-Jun and JunD and DNA binding properties of AP-1 proteins. Suppression of AP-1 activation by menin may be exerted through 2 independent mechanisms, direct inhibition on AP-1-mediated transcription and suppression of c-Fos induction. The molecular mechanism of inhibition of AP-1 function by menin needs further elucidation.
 ...
PMID:Suppression of insulin-induced AP-1 transactivation by menin accompanies inhibition of c-Fos induction. 1251 92

The gene responsible for multiple endocrine neoplasia type 1, MEN1, encodes the 610-amino acid-protein, menin. Although menin has been reported to bind AP-1 transcription factor JunD and suppress its transcriptional activity, little is known about its molecular mechanisms and physiological role. To better understand the function of menin and its significance in tumorigenesis, we investigated the effect of wild-type and mutant menin proteins on AP-1 transactivation. In COS cells, wild-type menin suppressed JunD-mediated transactivation in a dose-dependent manner, while it augmented c-Jun-mediated transactivation also in a dose-dependent manner. These effects were lost or reduced in all menin mutants examined. Electrophoretic mobility shift assay using AP-1 binding elements as a probe revealed that menin does not affect binding of c-Jun to DNA. Coexpression of menin mutants did not affect the function of wild-type menin. Coexpression of JunD amino-terminal fragment abolished menin-mediated enhancement of c-Jun transactivation, suggesting that Menin-JunD interaction may negatively regulate the enhancing effect of menin on c-Jun-mediated transactivation in COS cells.
 ...
PMID:JunD-menin interaction regulates c-Jun-mediated AP-1 transactivation. 1525 79

Menin is a tumor suppressor required to prevent multiple endocrine neoplasia in humans. Mammalian menin protein is associated with chromatin modifying complexes and has been shown to bind a number of nuclear proteins, including the transcription factor JunD. Menin shows bidirectional effects acting positively on c-Jun and negatively on JunD. We have produced protein null alleles of Drosophila menin (mnn1) and have over expressed the Mnn1 protein. Flies homozygous for protein-null mnn1 alleles are viable and fertile. Localized over-expression of Mnn1 causes defects in thoracic closure, a phenotype that sometimes results from insufficient Jun activity. We observed complex genetic interactions between mnn1 and jun in different developmental settings. Our data support the idea that one function of menin is to modulate Jun activity in a manner dependent on the cellular context.
 ...
PMID:Genetic interactions between Drosophila melanogaster menin and Jun/Fos. 1693 May 85