A novel nuclear RNA HSD52 scaffolding NONO/SFPQ complex modulates DNA damage repair to facilitate temozolomide resistance.

BACKGROUND: Temozolomide (TMZ) is used in the treatment of glioblastoma (GBM). However, the primary obstacle remains the emergence of TMZ chemotherapy resistance. Non-POU domain-containing octamer-binding protein (NONO) and splicing factor proline/glutamine rich (SFPQ) are multifunctional nuclear proteins involved in genome stability and gene regulation. However, the specific role of NONO and SFPQ in TMZ resistance of GBM remains to be explored.

METHODS: RNA-binding protein immunoprecipitation-microarray and RNA microarray of TMZ-resistant and parental cells were performed for the gain of HSD52. The effects of HSD52 on TMZ resistance were investigated through in vitro assays, intracranial xenograft, and GBM organoid models. The underlying mechanisms were explored by DNA methylation chip, RNA immunoprecipitation, RNA pull-down assays, among others. GBM clinical samples were rolled in to investigate the clinical significance of HSD52.

RESULTS: We identified a novel noncoding RNA, HSD52, that was highly expressed in TMZ-resistant GBM and facilitated the interaction between NONO and SFPQ. H3 ubiquitination attenuation and reduced DNA methyltransferase 1 (DNMT1) recruitment increased HSD52 transcription via DNA hypo-methylation. HSD52 formed an RNA duplex with UFM1 specific ligase 1 (UFL1) mRNA, thereby promoting NONO/SFPQ complex binding to UFL1 mRNA and enhancing its stability, and then contributed to TMZ resistance through activating the ataxia telangiectasia mutated signaling pathway. In vivo xenograft and GBM organoid models showed significant repression in tumor growth after HSD52 knockout with TMZ treatment. In GBM clinical samples, HSD52 was responsible for the malignant progression and TMZ resistance.

CONCLUSIONS: Our results revealed that HSD52 could serve as a promising therapeutic target to overcome TMZ resistance, improving the clinical efficacy of TMZ chemotherapy in GBM.