Small nucleolar RNA Sf-15 regulates proliferation and apoptosis of Spodoptera frugiperda Sf9 cells

Small nucleolar RNAs (snoRNAs) function in guiding 2′-O-methylation and pseudouridylation of ribosomal RNAs (rRNAs) and small nuclear RNAs (snRNAs). In recent years, more and more snoRNAs have been found to play novel roles in mRNA regulation, such as pre-mRNA splicing or RNA editing. In our previous study, we found a silkworm C/D box snoRNA Bm-15 can interact with Notch receptor gene in vitro. To further study the function of Bm-15, we cloned its homolog Sf-15 from Spodoptera frugiperda and investigate the function of Sf-15 in Sf9 cells.

We showed that knocking down of Sf-15 can inhibit the proliferation, then induce apoptosis of insect S. frugiperda Sf9 cells, but the results were reversed when Sf-15 was overexpressed. De novo sequencing of transcriptome of Sf9 cells showed that the expression of 21 apoptosis-related genes were increased upon Sf-15 repression. Further analysis showed that a Ca²⁺-induced cell death pathway gene Cn (PPP3C, the serine/threonine-protein phosphatase 2B catalytic subunit), was significantly increased upon Sf-15 depression but decreased when Sf-15 was overexpressed, which indicated that Cn might be a potential target of Sf-15.

We conclude that C/D box snoRNA Sf-15 can participate in apoptosis through regulating the expression of Ca²⁺-induced cell death pathway gene Cn in Sf9 cells. This is the first time that we found snoRNAs exhibiting dual functions in insect, which reveals a novel layer of ncRNA modulation in cell growth and death.