Fox K R, Marks J N, Waterloh K
Department of Physiology & Pharmacology, University of Southampton, UK.
Nucleic Acids Res. 1991 Dec 25;19(24):6725-30. doi: 10.1093/nar/19.24.6725.
We have studied the binding of echinomycin to DNA fragments containing GC-rich regions flanked by blocks of alternating AT by DNase I footprinting and diethylpyrocarbonate modification. Regions of alternating AT flanking the sequences CCCG, CCGC, CGGC and GG show a four base pair DNase I cleavage pattern and reaction of alternate adenines with diethylpyrocarbonate. This pattern is strongest when the AT-block is immediately adjacent to the CpG ligand binding site. We explain these phenomena by suggesting that echinomycin binds to the dinucleotide step ApT in a cooperative fashion. The cooperative effects can be transmitted through the dinucleotide step GC but not CC or AA. No such repetitive patterns are seen with surrounding regions of (ATT).(AAT). Evidence is presented for secondary drug binding sites at CpC and TpG with weaker interaction at the CpG site within the hexanucleotide TTCGAA.
我们通过DNA酶I足迹法和焦碳酸二乙酯修饰，研究了棘霉素与含有富含GC区域且两侧为交替AT序列块的DNA片段的结合情况。在序列CCCG、CCGC、CGGC和GG两侧的交替AT区域，呈现出四碱基对的DNA酶I切割模式以及交替腺嘌呤与焦碳酸二乙酯的反应。当AT序列块紧邻CpG配体结合位点时，这种模式最为明显。我们通过提出棘霉素以协同方式结合到二核苷酸步ApT来解释这些现象。协同效应可以通过二核苷酸步GC传递，但不能通过CC或AA传递。在(ATT).(AAT)的周围区域未观察到此类重复模式。有证据表明，在六核苷酸TTCGAA内的CpC和TpG处存在二级药物结合位点，且在CpG位点的相互作用较弱。
