Site 3 and site 4 from the factor X promoter bind Sp1/Sp3 from the liver.

(A) An oligonucleotide containing site 3 from the factor X promoter (−165 GTTCCCAGCGTGGTCACTCCCCTGCCTCGCCAG −132) was radiolabeled and incubated with 10 μg liver nuclear extracts. Lanes 2 to 6 contain molar excess of unlabeled competitor oligonucleotides from either site 3 itself or a consensus Sp1 binding site (5′ ATTCGATCGGGGCGGGGCGAGC 3′). Lanes 7 to 12 contain 2 μg antibodies against Sp1 and Sp3. (B) All lanes contain the same components as Figure 3A except that the probe was derived from site 4 (−191 TGCCTGGGGAAGGTGGGGCCAGAGTGG −169).