Fission Yeast Rad8/HLTF Facilitates Rad52-dependent Chromosomal Rearrangements Through PCNA Lysine 107 Ubiquitination

Rad52 recombinase can cause gross chromosomal rearrangements (GCRs). However, the mechanism of Rad52-dependent GCRs remains unclear. Here, we show that fission yeast Rad8/HLTF facilitates Rad52-dependent GCRs through the ubiquitination of lysine 107 (K107) of PCNA, a DNA sliding clamp. Loss of Rad8 reduced isochromosomes resulting from centromere inverted repeat recombination. Rad8 HIRAN and RING finger mutations reduced GCRs, suggesting that Rad8 facilitates GCRs through 3’ DNA-end binding and ubiquitin ligase activity. Mms2 and Ubc4 but not Ubc13 ubiquitin-conjugating proteins were required for GCRs. Consistent with this, PCNA K107R but not K164R mutation greatly reduced GCRs. Rad8-dependent PCNA K107 ubiquitination facilitates Rad52-dependent GCRs, as PCNA K107R, rad8 , and rad52 mutations epistatically reduced GCRs. Remarkably, K107 is located at the interface between PCNA subunits, and an interface mutation D150E bypassed the requirement of PCNA K107 ubiquitination for GCRs. This study uncovers the role of Rad8-dependent PCNA K107 ubiquitination in Rad52-dependent GCRs.