Nuclear Export Factor 3 Regulates Localization of Small Nucleolar RNAs

Small nucleolar RNAs (snoRNAs) guide chemical modifications of ribosomal and small nuclear RNAs, functions that are carried out in the nucleus. While most snoRNAs reside in the nucleolus, a growing body of evidence indicates that snoRNAs are also present in the cytoplasm and that snoRNAs move between the nucleus and cytoplasm by a mechanism that is regulated by lipotoxic and oxidative stress. Here, in a genome-wide shRNA-based screen, we identified nuclear export factor 3 (NXF3) as a transporter that alters the nucleocytoplasmic distribution of box C/D snoRNAs from the ribosomal protein L13a (Rpl13a) locus. Using RNA-sequencing analysis, we show that NXF3 associates not only with Rpl13a snoRNAs, but also with a broad range of box C/D and box H/ACA snoRNAs. Under homeostatic conditions, gain or loss of function of NXF3, but not related family member NXF1, decreases or increases cytosolic Rpl13a snoRNAs, respectively. Furthermore, treatment with the adenylyl cyclase activator forskolin diminishes cytosolic localization of the Rpl13a snoRNAs through a mechanism that is dependent on NXF3, but not NXF1. Our results provide evidence of a new role for NXF3 in regulating the distribution of snoRNAs between the nuclear and cytoplasmic compartments. Overall design: 3 input and 3 NXF3-immunoprecipitated RNA samples from NIH 3T3 mouse fibroblasts. NIH 3T3 cells were transfected with pEGFP-NXF3 plasmid and NXF3-GFP was immunoprecipitated using anti-GFP antibody from Abcam (catalog #ab290) bound to protein A-Dynabeads (Invitrogen).