||The universal deregulation of c-myc gene expression in tumor cells suggests that this oncogene represents an attractive target for cancer therapeutic purposes. The structural and biochemical features of the MYC family (MYC, N-MYC, and L-MYC) mark them as direct regulators of gene expression. As basic helix-loop-helix leucine zipper proteins (bHLH-ZIP), the MYCs acquire the capacity to bind the DNA sequence CACGTG (E-box) when dimerized with MAX (another bHLH-ZIP). A head-to- tail pair of MYC-MAX dimers may, in turn, form a heterotetramer capable of bridging distant E-boxes. Among the broadly distributed positive enforcers of MYC action that are often recruited to target genes are chromatin remodeling (SWI/SNF relatives) and modifying complexes (TRAPP/GCN5 and relatives); these complexes mobilize nucleosomes and acetylate histones and/or other targets to activate gene expression. MYC binds TBP along an auxiliary pathway to control gene expression. MAD and MNT generally oppose MYC action by enlisting histone deacetylase complexes. Besides acting at the level of chromatin, MYC may also operate at later stages of the transcription cycle, after pre-initiation complex formation. In addition to using generic chromatin complexes to up- or down-regulate transcription, the MYC network also conscripts individual factors to modify expression locally on an ad hoc basis. For example, YY1, AP2, MIZ1, SP1, BRCA1, and other proteins interact directly with MYC, and so may directly modify the output of the MYC network. Recombinant c-myc was expressed in a baculovirus system and purified by an affinity column in combination with FPLC chromatography. The purified recombinant protein is greater than 90% homogeneous and contains no detectable protease, DNase, and RNase activity.