Multifunctional protein that exhibits several independent functions at different levels of the cellular processes. 5'-3' exonuclease component of the nonsense-mediated mRNA decay (NMD) which is a highly conserved mRNA degradation pathway, an RNA surveillance system whose role is to identify and rid cells of mRNA with premature termination codons and thus prevents accumulation of potentially harmful truncated proteins. The NMD pathway has a second role regulating the decay of wild-type mRNAs, and especially mRNAs that are important for telomere functions. Participate in CTH2-mediated and VTS1-mediated mRNA turnover. Involved in the degradation of several hypomodified mature tRNA species and participates in the 5'-processing or the degradation of the snoRNA precursors and rRNA processing. Involved in defense against virus and suppresses viral RNA recombination by rapidly removing the 5'-truncated RNAs, the substrates of recombination, and thus reducing the chance for recombination to occur in the parental strain. Required for the assembly of the virus-like particles of the Ty3 retrotransposon and contributes to the efficient generation of narnavirus 20S RNA by playing a major role in the elimination of the non-viral upstream sequences from the primary transcripts. Degrades single-stranded DNA (ss-DNA) and can renature complementary ss-DNA as well as catalyzes the formation of heteroduplex DNA from circular ss-DNA and homologous linear ds-DNA in vitro. Acts as a microtubule-associated protein which interacts with cytoplasmic microtubules through beta-tubulin and promotes in vitro assembly of tubulin into microtubules. Associates with microtubule functions such as chromosome transmission, nuclear migration, and SPB duplication. Has also a role in G1 to S transition and is involved in nuclear fusion during karyogamy. Required for the expression of ROK1 at the post-transcriptional level and for the alpha-factor induction of the karyogamy genes KAR3 and KAR4. Plays a role in filamentous growth. Both strand exchange and nuclease activities require magnesium, for the strand exchange activity, calcium can replace magnesium when the linear ds-DNA has been first resected with an exogenous endonuclease. 3'-phosphoadenosine 5'-phosphate (pAp) is an inhibitor of KEM1. Sodium-induced GCN4 expression reduces pAp accumulation by activating HAL2 expression, and therefore maintains mRNA degradation capacity which is likely to be important for the accurate and rapid adaptation of gene expression to salt stress. Mutations affect nuclear fusion, leed to reduced chromosome stability and defects in spindle pole body duplication and/or separation as well as loss of viability under conditions of nitrogen starvation. Homozygous diploids are unable to sporulate. Leads also to arrest in pachytene and deficiency in meiotic recombination and sensitivity to oleate. Present with 11700 molecules/cell in log phase SD medium. Belongs to the 5'-3' exonuclease family.