RESUMO
The abnormal GGGGCC hexanucleotide repeat expansions (HREs) in C9orf72 cause the fatal neurodegenerative diseases including amyotrophic lateral sclerosis and frontotemporal dementia. The transcribed RNA HREs, short for r(G4C2)n, can form toxic RNA foci which sequestrate RNA binding proteins and impair RNA processing, ultimately leading to neurodegeneration. Here, we determined the crystal structure of r(G4C2)2, which folds into a parallel tetrameric G-quadruplex composed of two four-layer dimeric G-quadruplex via 5'-to-5' stacking in coordination with a K+ ion. Notably, the two C bases locate at 3'- end stack on the outer G-tetrad with the assistance of two additional K+ ions. The high-resolution structure reported here lays a foundation in understanding the mechanism of neurological toxicity of RNA HREs. Furthermore, the atomic details provide a structural basis for the development of potential therapeutic agents against the fatal neurodegenerative diseases ALS/FTD.
Assuntos
Esclerose Lateral Amiotrófica , Proteína C9orf72 , Expansão das Repetições de DNA , Demência Frontotemporal , Quadruplex G , RNA , Proteína C9orf72/genética , Proteína C9orf72/química , Esclerose Lateral Amiotrófica/genética , Demência Frontotemporal/genética , Humanos , RNA/química , RNA/genética , Expansão das Repetições de DNA/genética , Cristalografia por Raios X , Modelos MolecularesRESUMO
Guanine (G)-rich nucleic acid sequences can form diverse G-quadruplex structures located in functionally significant genome regions, exerting regulatory control over essential biological processes, including DNA replication in vivo. During the initiation of DNA replication, Cdc6 is recruited by the origin recognition complex (ORC) to target specific chromosomal DNA sequences. This study reveals that human Cdc6 interacts with G-quadruplex structure through a distinct region within the N-terminal intrinsically disordered region (IDR), encompassing residues 7-20. The binding region assumes a hook-type conformation, as elucidated by the NMR solution structure in complex with htel21T18. Significantly, mutagenesis and in vivo investigations confirm the highly specific nature of Cdc6's recognition of G-quadruplex. This research enhances our understanding of the fundamental mechanism governing the interaction between G-quadruplex and the N-terminal IDR region of Cdc6, shedding light on the intricate regulation of DNA replication processes.
Assuntos
DNA , Quadruplex G , Humanos , DNA/química , Replicação do DNA , Complexo de Reconhecimento de Origem/química , Complexo de Reconhecimento de Origem/genética , Complexo de Reconhecimento de Origem/metabolismo , Sequência de BasesRESUMO
The G-quadruplex (G4) forming C9orf72 GGGGCC (G4C2) expanded hexanucleotide repeat (EHR) is the predominant genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Developing selective G4-binding ligands is challenging due to the conformational polymorphism and similarity of G4 structures. We identified three first-in-class marine natural products, chrexanthomycin A (cA), chrexanthomycin B (cB), and chrexanthomycin C (cC), with remarkable bioactivities. Thereinto, cA shows the highest permeability and lowest cytotoxicity to live cells. NMR titration experiments and in silico analysis demonstrate that cA, cB, and cC selectively bind to DNA and RNA G4C2 G4s. Notably, cA and cC dramatically reduce G4C2 EHR-caused cell death, diminish G4C2 RNA foci in (G4C2)29-expressing Neuro2a cells, and significantly eliminate ROS in HT22 cells. In (G4C2)29-expressing Drosophila, cA and cC significantly rescue eye degeneration and improve locomotor deficits. Overall, our findings reveal that cA and cC are potential therapeutic agents deserving further clinical study.