The function of Ensembl gene identifier ENSG00000058729 (RIOK2, RIO kinase 2) is as follows. Serine/threonine-protein kinase involved in the final steps of cytoplasmic maturation of the 40S ribosomal subunit. Involved in export of the 40S pre-ribosome particles (pre-40S) from the nucleus to the cytoplasm. Its kinase activity is required for the release of NOB1, PNO1 and LTV1 from the late pre-40S and the processing of 18S-E pre- rRNA to the mature 18S rRNA (PubMed:19564402). Regulates the timing of the metaphase-anaphase transition during mitotic progression, and its phosphorylation, most likely by PLK1, regulates this function (PubMed:21880710). {ECO:0000269|PubMed:16037817, ECO:0000269|PubMed:19564402, ECO:0000269|PubMed:21880710}.