Myc-Nick
Myc-nick is a cytoplasmic form of Myc produced by a partial proteolytic cleavage of full-length c-Myc and N-Myc. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923036/pdf/nihms219804.pdf). Myc cleavage is mediated by the calpain family of calcium-dependent cytosolic proteases (http://en.wikipedia.org/wiki/Calpain).
The cleavage of Myc by calpains is a constitutive process, but is enhanced under conditions that require rapid downregulation of Myc levels, such as during terminal differentiation. Upon cleavage, the C-terminus of Myc (containing the DNA binding domain) is degraded, while Myc-nick, the N-terminal segment 298-residue segment remains in the cytoplasm. Myc-nick contains binding domains for histone acetyltransferases and for ubiquitin ligases.
The functions of Myc-nick are currently under investigation, but this new Myc family member was found to regulate cell morphology, at least in part, by interacting with acetyl transferases to promote the acetylation of α-tubulin. Ectopic expression of Myc-nick accelerates the differentiation of committed myoblasts into muscle cells.
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