Contractions of the C-Terminal Domain of Saccharomyces cerevisiae Rpb1p Are Mediated by Rad5p

We report that contractions require the post-replication repair factor Rad5p but, unlike expansions, not the homologous recombination factors Rad51p and Rad52p. Sequence analysis of contraction events reveals that deleted regions are flanked by microhomologies. We also find that G-quadruplex forming sequences predicted by the QGRS Mapper are enriched on the noncoding strand of the CTD compared to the body of RPB1. Formation of G-quadruplexes in the CTD coding region could block the replication fork, necessitating post-replication repair. We propose that contractions of the CTD result when microhomologies misalign during Rad5p-dependent template switching via fork reversal.
Source: G3: Genes Genomes Genetics - Category: Genetics & Stem Cells Authors: Tags: Investigations Source Type: research