EXO1: A tightly regulated nuclease.

Exonuclease 1 (EXO1) is an evolutionarily well conserved exonuclease. Its ability to resect DNA in the 5'-3' direction has been extensively characterized and shown to be implicated in several genomic DNA metabolic processes such as replication stress response, double strand break repair, mismatch repair, nucleotide excision repair and telomere maintenance. While the processing of DNA is critical for its repair, an excessive nucleolytic activity can lead to secondary lesions, increased genome instability and alterations in cellular functions. It is thus clear that different regulatory layers must be in effect to keep DNA degradation under control. Regulatory events that modulate EXO1 activity have been reported to act at different levels. Here we summarize the different post-translational modifications (PTMs) that affect EXO1 and discuss the implications of PTMs for EXO1 activities and how this regulation may be associated to cancer development.