Structural basis of the binding of metallo-antibiotic to GGGGCC hexanucleotide related structures seen in neurological diseases

• Main Authors: Cyong-Ru Jhan, 詹瓊如
• Other Authors: 侯明宏
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/99149318722336891455

碩士 === 國立中興大學 === 生命科學系所 === 104 === Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease that leads in the death of neuron. Recently, an expanded GGGGCC hexanucleotide repeats in the first intron of C9orf72 was found to be the most common cause of ALS and Frontotemporal dementia (FTD). The expanded GGGGCC DNA sequence is able to fold into stable G-quadruplex and hairpin structures which initiate ALS/FTD pathologies. One metallantibiotic, the Ni(II) complex of dimeric Chromomycin (Chro), has been docummented to function by groove binding to DNA at GC rich sites, thereby interrupting essential biological processes including replication and transcription. ALS are correlated with the expansion of d(GGGGCC)n hexanucleotide sequences, that provide many contiguous GGCC sites for Chro binding. This study focused on the biophysical characterization of the binding of the Ni(II) complex of dimeric Chro to DNA duplex with GGGGCC motif. Heat denaturation, circular dichroism and surface plasmon resonance analyses showed that duplex DNA with GGGGCC motif sequences are preferred Ni(II)(Chro)2-binding sites. Furthermore, we solved the crystal structure of Ni(II)(Chro)2 bound to d(TTGGGCCGAA/TTCGGCCCAA). The Chro dimer binds at and significantly widens the minor groove of the GGGCCG sequence. The long axis of each chromophore lies along and stacks over the sugar-phosphate backbone with the two attached saccharide moieties (rings A/B and C/D/E) wrapping across the minor groove. DNA is kinked by 22 degrees and 20 degrees in the two complexes, respectively. Six G-specific hydrogen bonds between Chro and DNA provide the GGGCCG sequence specificity. The binding of Ni(II)(Chro)2 to G-quadruplex structure of (GGGGCC)4 were further characterized by heat denaturation, circular dichroism and surface plasmon resonance analyses. The results showed that Ni(II)(Chro)2 is able to interact with the G-quadruplex structure of (GGGGCC)4 via 1:1 binding model. Our results provide evidence of a possible biological consequence of Ni(II)(Chro)2 binding to GGGGCC hexanucleotide repeat sequences.