DNA-binding protein and Mre11-Rad50-Xrs2 (MRX) complex activator; dsDNA binding protein that activates endo- and exonuclease activities of the MRX complex to initiate end resection during ds break repair and processing of DNA hairpin structures; role in telomere maintenance and formation of telomeric 3’ overhangs; solubility regulated by sumoylation and oligomeric state by phosphorylation; removal of active Sae2p triggered by DNA damage; sequence and functional similarity with human CtIP/RBBP8