Wechsler D S, Papoulas O, Dang C V, Kingston R E
Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Mol Cell Biol. 1994 Jun;14(6):4097-107. doi: 10.1128/mcb.14.6.4097-4107.1994.
The ability of a transcription factor to function in vivo must be determined in part by its ability to bind to its recognition site in chromatin. We have used Max and derivatives of c-Myc to characterize the effect of changes of dimerization partner on binding to nucleosomal DNA templates. We find that homo- and heterodimeric complexes of these proteins bind to the CACGTG sequence in free DNA with similar affinities. Although Max homodimers bind to nucleosomes, truncated c-Myc homodimers do not. Surprisingly, modifying the c-Myc dimerization interface or changing its dimerization partner to Max enables nucleosomal DNA binding. Thus, changes in dimer structure or dimerization efficiency can have significant effects on nucleosome binding that are not predicted from their affinity for free DNA. We conclude that domains other than the basic region per se influence the ability of a transcription factor to bind to nucleosomal DNA and that changes of dimerization partner can directly affect the ability of a factor to occupy nucleosomal binding sites.
转录因子在体内发挥功能的能力，在一定程度上必须由其与染色质中识别位点结合的能力来决定。我们利用Max和c-Myc的衍生物来表征二聚化伙伴的变化对与核小体DNA模板结合的影响。我们发现，这些蛋白质的同二聚体和异二聚体复合物以相似的亲和力与游离DNA中的CACGTG序列结合。虽然Max同二聚体可与核小体结合，但截短的c-Myc同二聚体则不能。令人惊讶的是，修饰c-Myc二聚化界面或将其二聚化伙伴换成Max可实现与核小体DNA的结合。因此，二聚体结构或二聚化效率的变化可对核小体结合产生显著影响，而这些影响无法从它们对游离DNA的亲和力中预测出来。我们得出结论，除了基本区域本身之外，其他结构域也会影响转录因子与核小体DNA结合的能力，并且二聚化伙伴的变化可直接影响一个因子占据核小体结合位点的能力。
