Dimerization of FIR upon FUSE DNA binding suggests a mechanism of c-myc inhibition.
c-myc is essential for cell homeostasis and growth but lethal if improperly regulated. Transcription of this oncogene is governed by the counterbalancing forces of two proteins on TFIIH--the FUSE binding protein (FBP) and the FBP-interacting repressor (FIR). FBP and FIR recognize single-stranded DNA upstream of the P1 promoter, known as FUSE, and influence transcription by oppositely regulating TFIIH at the promoter site. Size exclusion chromatography coupled with light scattering reveals that an FIR dimer binds one molecule of single-stranded DNA. The crystal structure confirms that FIR binds FUSE as a dimer, and only the N-terminal RRM domain participates in nucleic acid recognition. Site-directed mutations of conserved residues in the first RRM domain reduce FIR's affinity for FUSE, while analogous mutations in the second RRM domain either destabilize the protein or have no effect on DNA binding. Oppositely oriented DNA on parallel binding sites of the FIR dimer results in spooling of a single strand of bound DNA, and suggests a mechanism for c-myc transcriptional control.
Crichlow
Gregg V
GV
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA.
Zhou
Hongwen
H
Hsiao
Hsin-hao
HH
Frederick
Kendra B
KB
Debrosse
Maxime
M
Yang
Yuande
Y
Folta-Stogniew
Ewa J
EJ
Chung
Hye-Jung
HJ
Fan
Chengpeng
C
De la Cruz
Enrique M
EM
Levens
David
D
Lolis
Elias
E
Braddock
Demetrios
D
D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D029721:Drosophila Proteins / Q000737:chemistry; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011485:Protein Binding / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism*; D051758:Transcription Factor TFIIH / Q000378:metabolism
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C492258:FUBP1 protein, human; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C410595:poly-U binding splicing factor 60KDa; D051758:Transcription Factor TFIIH; D004247:DNA; D004265:DNA Helicases