The FUSE/FBP/FIR/TFIIH system is a molecular machine programming a pulse of c-myc expression.
FarUpStream Element (FUSE) Binding Protein (FBP) binds the human c-myc FUSE in vitro only in single-stranded or supercoiled DNA. Because transcriptionally generated torsion melts FUSE in vitro even in linear DNA, and FBP/FBP Interacting Repressor (FIR) regulates transcription through TFIIH, these components have been speculated to be the mechanosensor (FUSE) and effectors (FBP/FIR) of a real-time mechanism controlling c-myc transcription. To ascertain whether the FUSE/FBP/FIR system operates according to this hypothesis in vivo, the flux of activators, repressors and chromatin remodeling complexes on the c-myc promoter was monitored throughout the serum-induced pulse of transcription. After transcription was switched on by conventional factors and chromatin regulators, FBP and FIR were recruited and established a dynamically remodeled loop with TFIIH at the P2 promoter. In XPB cells carrying mutant TFIIH, loop formation failed and the serum response was abnormal; RNAi depletion of FIR similarly disabled c-myc regulation. Engineering FUSE into episomal vectors predictably re-programmed metallothionein-promoter-driven reporter expression. The in vitro recruitment of FBP and FIR to dynamically stressed c-myc DNA paralleled the in vivo process.
Liu
Juhong
J
Laboratory of Pathology, National Cancer Institute, Bethesda, MD 20892-1500, USA.
Kouzine
Fedor
F
Nie
Zuqin
Z
Chung
Hye-Jung
HJ
Elisha-Feil
Zichrini
Z
Weber
Achim
A
Zhao
Keji
K
Levens
David
D
D002460:Cell Line; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D051758:Transcription Factor TFIIH / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D002843:Chromatin; D004278:DNA, Superhelical; C491053:MT2A protein, human; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; C410595:poly-U binding splicing factor 60KDa; D051758:Transcription Factor TFIIH; D008668:Metallothionein