Identification and targeting of G-quadruplex structures in MALAT1 long non-coding RNA

RNA G-quadruplexes (rG4s) have functional roles in many cellular processes in diverse organisms. While a number of rG4 examples have been reported in coding messenger RNAs (mRNA), so far only limited works have studied rG4s in non-coding RNAs (ncRNAs), especially in long non-coding RNAs (lncRNAs) that are of emerging interest and significance in biology. Herein, we report that MALAT1 lncRNA contains conserved rG4 motifs, forming thermostable rG4 structures with parallel topology. We also show that rG4s in MALAT1 lncRNA can interact with NONO protein with high specificity and affinity in vitro and in nuclear cell lysate, and we provide in vivo data to support that NONO protein recognizes MALAT1 lncRNA via rG4 motifs. Notably, we demonstrate that rG4s in MALAT1 lncRNA can be targeted by rG4-specific small molecule, peptide, and L-aptamer, leading to the dissociation of MALAT1 rG4-NONO protein interaction. Altogether, this study uncovers new and important rG4s in MALAT1 lncRNAs, reveals their specific interactions with NONO protein, offers multiple strategies for targeting MALAT1 and its RNA-protein complex via its rG4 structure, and illustrates the prevalence and significance of rG4s in ncRNAs.