RNA G-quadruplex in live cells lighted-up by a thiazole orange analogue for SCA36 identification

SCA36 is a neurodegenerative disease mainly caused by the abnormal expansion of the GGGCCT repeat sequence in intron 1 of NOP56. The RNA sequences of this gene are expected to form large amounts of G-quadruplexes in the cytoplasm, which may be a potential intervention and detection target for SCA36. Here, we have developed a small-molecular compound named TCB-1, which shows good selectivity to the G-quadruplex structure, and its fluorescence can be enhanced by hundreds of folds. Interestingly, TCB-1 can avoid lysosome capture, evenly disperse in the cytoplasm, and selectively light up the cytoplasmic RNA G-quadruplexes. This property allows TCB-1 to sensitively detect the increased formation of cytoplasmic RNA G-quadruplexes in SCA36 model cells. This work not only provides new ideas for the design of small-molecule compounds targeting RNA G-quadruplexes in living cells, but also intuitively demonstrates the increased formation of RNA G-quadruplexes caused by NOP56 gene mutation, providing a possible tool for the detection of SCA36.

Automated summary

SCA36 is caused by abnormal expansion of the GGGCCT repeat sequence in NOP56 intron 1, leading to the increased formation of RNA G-quadruplexes. The small-molecule compound TCB-1 has been developed as a selective and fluorescent probe for RNA G-quadruplexes, which can be used to sensitively detect cytoplasmic RNA G-quadruplexes in SCA36 model cells. This study not only offers new insights for designing small-molecule compounds targeting RNA G-quadruplexes in living cells, but also provides a potential tool for detecting SCA36 by demonstrating the increased formation of RNA G-quadruplexes caused by NOP56 gene mutation.