N-Myc
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N-myc proto-oncogene protein also known as N-Myc or basic helix-loop-helix protein 37 (bHLHe37), is a
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''MYCN''
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.


Function

The ''MYCN'' gene is a member of the MYC family of
transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
s and encodes a protein with a basic helix-loop-helix ( bHLH) domain. This protein is located in the cell nucleus and must dimerize with another bHLH protein in order to bind DNA. N-Myc is highly expressed in the fetal brain and is critical for normal brain development. The ''MYCN'' gene has an antisense RNA, N-cym or ''MYCNOS'', transcribed from the opposite strand which can be translated to form a protein product. N-Myc and ''MYCNOS'' are co-regulated both in normal development and in tumor cells, so it is possible that the two transcripts are functionally related. It has been shown that the antisense RNA encodes for a protein, named NCYM, that has originated ''de novo'' and is specific to human and chimpanzee. This NCYM protein inhibits GSK3b and thus prevents MYCN degradation. Transgenic mice that harbor human MYCN/NCYM pair often show neuroblastomas with distant metastasis, which are atypical for normal mice. Thus NCYM represents a rare example of a de novo gene that has acquired molecular function and plays a major role in
oncogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abno ...
.


Clinical significance

Amplification and overexpression of N-Myc can lead to tumorigenesis. Excess N-Myc is associated with a variety of tumors, most notably
neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the head, neck, chest, abdomen, or Vertebral column, spine. Symptoms may include ...
s where patients with amplification of the N-Myc gene tend to have poor outcomes. MYCN can also be activated in neuroblastoma and other cancers through somatic mutation. Intriguingly, recent genome-wide H3K27ac profiling in patient-derived NB samples revealed four distinct SE-driven epigenetic subtypes, characterized by their own and specific master regulatory networks. Three of them are named after the known clinical groups: MYCN-amplified, MYCN non-amplified high-risk, and MYCN non-amplified low-risk NBs, while the fourth displays cellular features which resemble multipotent Schwann cell precursors. Interestingly, the cyclin gene CCND1 was regulated through distinct and shared SEs in the different subtypes, and, more importantly, some tumors showed signals belonging to multiple epigenetic signatures, suggesting that the epigenetic landscape is likely to contribute to intratumoral heterogeneity.


Interactions

N-Myc has been shown to interact with
MAX Max or MAX may refer to: Animals * Max (American dog) (1983–2013), at one time purported to be the world's oldest living dog * Max (British dog), the first pet dog to win the PDSA Order of Merit (animal equivalent of the OBE) * Max (gorilla) ...
. N-Myc is also stabilized by aurora A which protects it from degradation. Drugs that target this interaction are under development, and are designed to change the conformation of aurora A. Conformational change in Aurora A leads to release of N-Myc, which is then degraded in a
ubiquitin Ubiquitin is a small (8.6  kDa) regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ''ubiquitously''. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 19 ...
-dependent manner. Being independent from MYCN/MAX interaction, MYCN is also a transcriptional co-regulator of p53 in MYCN-amplified neuroblastoma. MYCN alters transcription of p53 target genes which regulate apoptosis responses and DNA damage repair in cell cycle. This MYCN-p53 interaction is through exclusive binding of MYCN to C-terminal domains of tetrameric p53. As a post-translational modification, MYCN binding to C-terminal domains of tetrameric p53 impacts p53 promoter selectivity and interferes other cofactors binding to this region.


See also

* Myc


References


Further reading

* * * * * * * * * * * * * * * * * *


External links

* {{Transcription factors, g1 Transcription factors Human proteins