Serine/threonine kinase involved in the regulation of MAPK signaling. Is an activator of the ERK1/2 signaling cascade playing an essential role in the stimulation of oocyte maturation. {ECO:0000269|PubMed:34779126, ECO:0000269|PubMed:34997960, ECO:0000269|PubMed:35670744}. This is the function of MOS (MOS proto-oncogene, serine/threonine kinase, Ensembl gene identifier ENSG00000172680).