MOLECULAR-BASIS FOR SEQUENCE-SPECIFIC DNA ALKYLATION BY CC-1065
MOLECULAR-BASIS FOR SEQUENCE-SPECIFIC DNA ALKYLATION BY CC-1065
复制标题
DOI：
10.1021/bi00410a054
复制
发表时间：
1988-05-17
期刊：
影响因子：
2.9
通讯作者：
ARISTOFF, PA
中科院分区：
文献类型：
--
作者：
HURLEY, LH;LEE, CS;ARISTOFF, PA
CC-1065是一种有效的抗肿瘤抗生素，它与DNA小凹槽中的腺嘌呤N3共价结合。CC-1065分子由三个重复的吡咯吲哚亚基组成，其中一个（左边的一个或A亚基）含有活性环丙基功能。该药物以高度序列特异性的方式与DNA中的腺嘌呤反应，将四个碱基对重叠到共价修饰碱基的5'侧。伴随CC-1065与DNA的共价结合而来的是对局部DNA结构的不对称影响，它向共价结合位点的5”侧延伸了多个螺旋。评估了CC-1065和一组三聚体合成类似物的DNA烷基化，序列特异性和生物效力。结果表明：(a)这一系列化合物与DNA之间的非共价相互作用不会导致形成足够稳定的配合物，无法通过足迹方法检测；(b)序列特异性和烷基化强度可以通过非反应性中间和右手段上的取代基来调节；(c)生物效力与烷基化DNA的能力密切相关。此外，我们还比较了CC-1065烷基化亚基与0（类似物A）、1（类似物AB）或2（类似物ABC）非反应性吲哚亚基组成的三种类似物与线性DNA片段之间共价加合物形成的程度和序列特异性。结果表明，该类似物系列共价结合的特异性不是由B和C亚基与次要凹槽的非共价相互作用控制，而是由腺嘌呤与烷基化(A)亚基的序列依赖性反应性控制。然而，B和C亚基显著增加了与“易感”腺嘌呤反应的表观速率常数，表明这些部分在形成共价键之前促进了非共价相互作用。仅由CC-1065烷基化亚基组成的类似物（类似物A）的共价结合与整个CC-1065分子对DNA结构的不对称效应相同。这种局部DNA结构的改变可能是加合物形成的结果。或者，它可能是在共价键形成之前存在的特定DNA构象的间接证据，并且被药物“捕获”。有人提出，某些含腺嘌呤的序列更倾向于经历这种局部构象变化，这是这些dna反应性化合物序列特异性的分子基础。这些结果提供了强有力的实验证据，证明序列依赖位点反应性的重要性，而不是非共价次要槽相互作用，在确定一些dna反应性分子的烷基化特异性方面。
CC-1065 is a potent antitumor antibiotic that binds covalently to N3 of adenine in the minor groove of DNA. The CC-1065 molecule is made up of three repeating pyrroloindole subunits, one of which (the left-hand one or A subunit) contains a reactive cyclopropyl function. The drug reacts with adenines in DNA in a highly sequence-specific manner, overlapping four base pairs to the 5'' side of the covalently modified base. Concomitant with CC-1065 covalent binding to DNA is an asymmetric effect on local DNA structure which extends more than one helix turn to the 5''-side of the covalent binding site. The DNA alkylation, sequence specificity, and biological potency of CC-1065 and a select group of trimeric synthetic analogues were evaluated. The results suggest that (a) noncovalent interactions between this series of compounds and DNA do not lead to the formation of complexes stable enough to be detected by footprinting methods, (b) sequence specificity and alkylation intensity can be modulated by the substituents on the nonreactive middle and right-hand segments and (c) biological potency correlates well with ability to alkylate DNA. In addition, the extent and the sequence specificity of covalent adduct formation between linear DNA fragments and three analogues comprised of the CC-1065 alkylating subunit linked to zero (analogue A), one (analogue AB), or two (analogue ABC) nonreactive indole subunits were compared. The results suggest that specificity of covalent binding of this analogue series is controlled not by the noncovalent interactions of the B and C subunits with the minor groove but by sequence-dependent reactivity of adenines with the alkylating (A) subuint. However, the B and C subunits markedly increase the apparent rate constant of the reaction with "susceptible'' adenines, suggesting that these moieties facilitate noncovalent interactions preceding covalent bond formation. Covalent binding of the analogue consisting only of the alkylating subunit of CC-1065 (analogue A) was associated with the same large asymmetric effect on DNA structure as the entire CC-1065 molecule. This altered local DNA structure could be a consequence of adduct formation. Alternatively, it may be indirect evidence of a particular DNA conformation which existed prior to covalent bond formation and which was "trapped by the drug. It is proposed that certain adenine-containing sequences have an increased propensity to undergo such a local conformational change and that this is the molecular basis for sequence specificy of these DNA-reactive compounds. The results provide strong experimental evidence for the importance of sequence-dependent site reactivity, rather than noncovalent minor groove interactions, in determining the alkylation specificity of some DNA-reactive molecules.