Putative nuclease that forms a complex with Pbp1p; involved in posttranscriptional regulation of HO, propagation of M2 dsRNA satellite of L-A virus; allelic variation affects mitochondrial genome stability, drug resistance, stress responses through posttranscriptional modulation of Puf3p targets; forms cytoplasmic foci upon DNA replication stress; localization to P-bodies under ethanol stress differs between strains