A c-myc tag is a polypeptide tag derived from the c-myc gene product and is often used in affinity chromatography for protein purification or for immunodetection of corresponding fusion proteins with an anti-myc antibody. The c-myc peptide spans the eleven amino acid sequence EQKLISEEDL and is a relatively small protein-tag, therefore.

c-Myc is a protein that functions as a transcription factor activating the expression of targeted genes upon hetero-dimerisation with an obligate partner. Direct and indirect target genes comprise genes that are involved in cell growth, cell differentiation and apoptosis.

The c-myc oncogene is among the most frequently overexpressed genes in human cancer