Abstract
ME1a1, a 16-base-pair nuclear factor binding site residing between the c-MYC P1 and P2 transcription initiation sites, is required for P2 activity. A cDNA encoding a 477-amino acid zinc finger protein designated MAZ (MYC-associated zinc finger protein) was cloned from a HeLa lambda gt11 library by screening with a concatamerized ME1a1 binding site probe. In addition to six potential zinc fingers of the Cys2His2 type, MAZ contains an amino-terminal proline-rich domain and several polyalanine tracts. Its mRNA was present in all human tissues tested except for kidney, as a doublet of approximately 2.5 and 2.7 kilobases, along with differentially expressed minor species. MAZ bound specifically to the wild-type ME1a1 sequence but not to a ME1a1 mutant that also failed to yield P2 activity. When expressed as a fusion protein in a pMAL-c vector, MAZ binds with specificity to a GA box sequence (GGGAGGG) found in the c-MYC P2 promoter, to the P2 attenuator region within the gene's first exon, and to a related sequence involved in the transcriptional termination of the C2 gene. MAZ may encode a transcription factor with dual roles in transcription initiation and termination.