Genomic information is vital for the survival and reproduction of all living cells. The integrity of DNA is frequently challenged by damaging agents like ultraviolet (UV) radiation, which can ultimately lead to mutation and disease. The DNA Damage Response (DDR) is at the front lines of genomic defense, acting to promote recognition and repair of DNA lesions. A critical consequence of the DDR is a transient decrease in the levels of RNA Polymerase II (Pol II) and mRNA, during which time the cell can repair transcribed regions of the genome. UV irradiation of human cells reduces mRNA at least in part by inhibiting RNA 3’ processing, and processing factors likewise promote Pol II ubiquitination and degradation. These data indicate that 3’ processing factors provide an important link to the DDR, but the scope and mechanism of these interactions are as yet unknown.
Our labs have previously shown that UV-induced inhibition of RNA processing is a conserved response in yeast, and UV-type damage induces genome-wide variation in poly(A) sites. We sought to identify additional functional links between 3’ processing factors and the DDR in the yeast model system in order to better characterize the mechanism of coordination. We have observed that yeast 3’ processing mutants are sensitive to UV-type DNA damaging agents. Yeast 3’ processing mutants exhibit unique genetic interactions with nucleotide excision repair mutants but not with factors in homologous recombination or post-replication repair pathways. Yeast 3’ processing mutants also impair the ubiquitination and degradation of Pol II following DNA damage. In ongoing experiments we are testing the role of 3’ processing factors in the recruitment of ubiquitination and DNA repair machineries following UV damage. Overall these results suggest that 3’ processing factors promote DNA repair by removing Pol II stalled at UV-type DNA lesions, a functional interaction that is conserved between yeast and human cells.