Structural analysis of the chicken max gene.

The recent identification of Max, a nuclear phosphoprotein that dimerizes with members of the Myc protein family, has provided an additional tool to examine the role of the Myc oncoprotein as a sequence-specific DNA binding protein and a potential regulator of gene transcription. Here we report the nucleotide sequence of an avian max gene isolated from a lambda EMBL3 genomic library prepared from size-selected chicken embryo fibroblast DNA. The complete transcription unit encoding chicken Max is contained on a 5.7 kbp BglII DNA fragment which expresses an appropriately sized max mRNA of 1.5 kb following transfection of C3H10T1/2 mouse fibroblasts. The coding region of the chicken max gene is organized into five exons and the overall identity between the human and chicken max coding sequences is 85% at the nucleotide level and 96% at the amino acid level. The basic helix-loop-helix/leucine zipper region, the casein kinase II phosphorylation sites and the nuclear localization signal sequence are 100% conserved in all vertebrate Max proteins characterized to date. DNA sequence analysis of the 5' flanking region of the chicken max coding sequence reveals the absence of consensus TATA or CAAT motifs, but the presence of numerous GC-rich sequences that are typical in eukaryotic genes which are expressed constitutively in different tissues and under different growth conditions.