Poly (ADP-ribose) polymerase in yeasts: characterization and involvement in telomere maintenance.

Poly (ADP-ribose) polymerases (PARPs) are enzymes catalyzing the post-translational addition of chains of ADP-ribose moieties to proteins. In most eukaryotic cells, their primary protein targets are involved in DNA recombination, repair, and chromosome maintenance. Even though this group of enzymes is quite common in both eukaryotes and prokaryotes, no PARP homologs have been described so far in ascomycetous yeasts, leaving their potential roles in this group of organisms unexplored. Here, we characterize Pyl1 protein of Yarrowia lipolytica as the first candidate of PARP in yeasts. We show that the expression of PYL1 gene is increased in mutants lacking either subunit of telomerase and identified several of its candidate protein targets in vivo. We demonstrate that Pyl1p is a functional PARP that undergoes auto-PARylation and PARylates YlKu70/80 complex. We also show that overexpression of PYL1 in Y. lipolytica cells results in dissociation of YlKu80 from telomeres in vivo, supporting the role of Pyl1p in telomere protection and maintenance. Based on our observations, we propose Pyl1p and its homologs identified in other yeast species represent a distinct class of PARPs, thus substantiating a more detailed investigation of their roles in these organisms.