Sequence‐specific DNA‐binding proteins which interact with (G + C)‐rich sequences flanking the chicken c‐myc gene

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Abstract
The interaction of nuclear sequence-specific DNA-binding proteins from definitive chicken erythrocytes, thymus and proliferating transformed erythroid precursor (HD3) cells with the 700-base-pair (700-bp) DNA 5''-flanking region of the chicken c-myc gene was investigated by in vitro footprint analysis. The major HD3 protein-binding activity binds to a site (site V) 200 bp upstream from the ''cap'' site but, after further fractionation, a second distinct binding activity is detected at a site (site VIII) which contains both the ''CAAT'' and ''SP1-binding'' consensus sequences. Protein from thymus and erythrocytes cells which express c-myc at lower levels, bind to seven and eight sites respectively. In common with HD3 cell prtein, they both bind to site VIII and, although binding to the sequence at site V is also detected, the footprint protection pattern is sufficiently different (site V'') to suggest the involvement of different proteins in terminally differentiated and proliferating cells. The DNA-binding activities were partially fractionated by high-performance liquid chromatography gel filtration and include an erythrocyte-specific protein which binds to a c-myc gene poly(dG) homopolymer sequence similar to that found upstream of the chicken .beta.A-globin gene.