Effects of site-specific guanine C8-modifications on an intramolecular DNA G-quadruplex.
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ABSTRACT:
SUBMITTER: Lech CJ
PROVIDER: S-EPMC3192963 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:DNA sequences of high guanine (G) content have the potential to fold into G quadruplex (G4) structures. DNA G4 is known to play important roles in various cellular processes including DNA replication, transcriptional regulation, and maintenance of genomic integrity. A more complete understanding about the biological functions of G4 DNA requires the investigation about how these structures are recognized by cellular proteins. Here, we conducted exhaustive quantitative proteomic experiments to profile the interaction proteomes of three well-defined G4 structures derived from the human telomere and the promoters of cMYC and cKIT genes. Our results led to the identification of a number of candidate G4-interacting proteins; some were previously reported, e.g., FUS, TOP1, and PARP1, and many others were discovered here for the first time. These included three proteins that can bind to all three DNA G4 structures and many proteins that can bind specifically to selected DNA G4 structure(s). We also validated that GRSF1 can bind directly and selectively toward G4 DNA structure derived from the cMYC promoter. Taken together, we uncovered a number of cellular proteins that exhibit general and selective recognitions of G4 folding patterns, which underscore the complexity of G4 DNA in biology and the importance in understanding fully the G4-interaction proteome.
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Project description:In the presence of monovalent alkali metal ions, G-rich DNA sequences containing four runs of contiguous guanines can fold into G-quadruplex (G4) structures. Recent studies showed that these structures are located in critical regions of the human genome and assume important functions in many essential DNA metabolic processes, including replication, transcription and repair. However, not all potential G4-forming sequences are actually folded into G4 structures in cells, where G4 structures are known to be dynamic and modulated by G4-binding proteins as well as helicases. It remains unclear whether there are other factors influencing the formation and stability of G4 structures in cells. Herein, we showed that DNA G4s can undergo phase separation in vitro. In addition, immunofluorescence microscopy and ChIP-Seq experiments with the use of BG4, a G4 structure-specific antibody, revealed that disruption of phase separation in cells could result in global destabilization of G4 structures. Together, our work revealed phase separation as a new determinant in regulating the formation and stability of G4 structures in human cells.
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