Identification of amino acid-base contacts in the Myc-DNA complex by site-specific bromouracil mediated photocrosslinking.

Myc binds to a 6 bp 2-fold symmetric DNA site: 5'-C-3A-2C-1G+1T+2G+3-3'. Using site-specific 5-bromouracil mediated photocrosslinking, we show that His336 of Myc contacts, or is close to, the thymine 5-methyl group at 2-fold symmetry-related positions -2 and +2 of the DNA site in the Myc-DNA complex. Our results strongly suggest that homologous amino acids of Myc and Max make equivalent contacts in the respective protein-DNA complexes.