Atypical U3 snoRNA Suppresses the Process of Pterygia through Modulating 18S Ribosomal RNA Synthesis

Ribosome biosynthesis plays a crucial role in regulating protein translation and is essential for cell growth and development in physiological progress. The progression and recurrence of Pterygia mainly occur due to the abnormal proliferation and migration of stromal Pterygia fibroblasts. Small nucleolar RNA U3 (U3 snoRNA), harboring the atypical C/D boxes, is involved in 18S ribosomal RNA (18S rRNA) synthesis; however, the mechanism of U3 snoRNA in Pterygia remains unclear. Methods: Primary HCFs and HPFs were separated and cultured from fresh conjunctival grafts and Pterygia tissues. The PLKO.1 lentiviral system and CRISPR/Cas9 recombinant construct were, respectively, used to overexpress and silence U3 snoRNA in HPF and HCF cells for further specific phenotypes analysis. RNA-seq and TMT-labeled quantitative protein mass spectrometry were utilized to evaluate the effect of U3 snoRNA on mRNA transcripts and protein synthesis. Results: Reduced U3 snoRNA in Pterygia promotes HCF or HPF cells' proliferation, migration, and cell cycle but has no significant effect on apoptosis. U3 snoRNA modulates 18S rRNA synthesis through shearing precursor ribosomal RNA 47S rRNA at the 5′ external transcribed spacer (5′ ETS). Moreover, the altered U3 snoRNA causes mRNA and protein differential expression in HCF or HPF cells. Conclusion: The atypical U3 snoRNA regulates the translation of specific proteins to exert a suppressive function in Pterygia through modulating the 18S RNA synthesis. Here, we uncover a novel insight into U3 snoRNA biology in the development of Pterygia.