He L, Liu J, Collins I, Sanford S, O'Connell B, Benham C J, Levens D
Laboratory of Pathology, DCS, NCI, Building 10, Room 2N105, Bethesda, MD 20892-1500, USA.
EMBO J. 2000 Mar 1;19(5):1034-44. doi: 10.1093/emboj/19.5.1034.
The c-myc regulatory region includes binding sites for a large set of transcription factors. The present studies demonstrate that in the absence of FBP [far upstream element (FUSE)-binding protein], which binds to the single-stranded FUSE, the remainder of the set fails to sustain endogenous c-myc expression. A dominant-negative FBP DNA-binding domain lacking effector activity or an antisense FBP RNA, expressed via replication-defective adenovirus vectors, arrested cellular proliferation and extinguished native c-myc transcription from the P1 and P2 promoters. The dominant-negative FBP initially augmented the single-stranded character of FUSE; however, once c-myc expression was abolished, melting at FUSE could no longer be supported. In contrast, with antisense FBP RNA, the single-stranded character of FUSE decreased monotonically as the transcription of endogenous c-myc declined. Because transcription is the major source of super-coiling in vivo, we propose that by binding torsionally strained DNA, FBP measures promoter activity directly. We also show that FUSE is predicted to behave as a torsion-regulated switch poised to regulate c-myc and to confer a higher order regulation on a large repertoire of factors.
c-myc调控区域包含大量转录因子的结合位点。目前的研究表明，在缺乏与单链FUSE结合的FBP[远上游元件（FUSE）结合蛋白]时，该组中的其他因子无法维持内源性c-myc的表达。通过复制缺陷型腺病毒载体表达的缺乏效应活性的显性负性FBP DNA结合结构域或反义FBP RNA，可阻止细胞增殖并消除来自P1和P2启动子的天然c-myc转录。显性负性FBP最初增强了FUSE的单链特性；然而，一旦c-myc表达被消除，FUSE处的解链就不再能得到支持。相反，对于反义FBP RNA，随着内源性c-myc转录的下降，FUSE的单链特性单调降低。因为转录是体内超螺旋的主要来源，我们提出FBP通过结合扭曲应变的DNA直接测量启动子活性。我们还表明，预计FUSE表现为一个扭转调节开关，随时准备调节c-myc并对大量因子赋予更高层次的调节。
