MiR-662 impairs C/D box snoRNA expression and rRNA 2'-O-ribose methylation marks.

BACKGROUND: MiR-662 overexpression has been reported to promote breast cancer metastatic progression and to impair the expression of genes encoding for proteins involved in translation, ribosome biogenesis and ribosome processing (Puppo et al., 2023); however, the relationship between miR-662 and the translational machinery was not further investigated at the time. METHODS: MiR-662 was overexpressed in MDA-MB-231-luc2 (NW1) human breast cancer cells. Global protein synthesis was analyzed using polysome profiles. Potential defects in rRNA 47S precursor biogenesis were evaluated by Northern blot. C/D box snoRNA (SNORD) expression was quantified by a medium-throughput RT-qPCR microfluidic dynamic array. rRNA 2'O-ribose methylation (2'Ome) was profiled using RiboMethSeq. RESULTS: No changes in rRNA synthesis, processing, or maturation were observed upon miR-662 overexpression. In contrast, a marked reduction in the ratio of polysomal to free ribosomal fractions was observed, indicating an impaired mRNA engagement into translation. Interestingly, a drastic decrease in SNORD levels (but not of their host genes) and a global decrease in rRNA 2'Ome was observed upon miR-662 overexpression. CONCLUSIONS: The involvement of miRNAs in snoRNA-induced modulation in rRNA epitranscriptomic marks might be a novel mechanism of fine regulation of the ribosome composition with possible repercussions on breast cancer metastatic progression.