UV irradiation, DNA damage and alternative splicing

MANUEL J. MUÑOZ; NICOLÁS NIETO MORENO; GWENDAL DUJARDIN; LUCIANA E. GIONO; ALBERTO R. KORNBLIHTT

Cabo Sounio

Conferencia; EMBO Conference: The DNA damage response in cell physiology and disease; 2013

EMBO

UV mutagenesis is a critical step in the generation of different forms of skin cancer. However, the relative contribution to the transcriptional/DNA damage response of the most conspicuous UV-induced DNA lesions, i.e., cyclobutane pyrimidine dimers (CPD) and 6-4 pyrimidine-pyrimidone photoproducts (6-4 PP), is unclear. It has been recently shown that UVB radiation (302 nm), which is the most harmful solar radiation that reaches the Earth's surface, induces higher CPD/6-4 PP ratios than UVC. Although both lesions are removed by NER (Nucleotide Excision Repair), the different half-lifes of CPDs (≈24 hs) compared to 6-4 PPs (≈2 hs) suggest that the recognition of both lesions, and may be the signaling generated thereafter, are not the same. We have previously shown that UV irradiation (UVC, 254 nm) causes the hyperphosphorylation of the carboxy terminal domain (CTD) of RNA polymerase II (pol II) large subunit, which slows transcriptional elongation rate and affects alternative splicing of a subset of genes through the kinetic coupling of transcription and splicing. We have compared the response of human keratinocytes in culture to UVC and UVB treatment using doses that generate comparable CPD amounts. RNA-seq global analysis of control, UVC- and UVB-treated cells revealed that transcriptional down-regulation and higher exon inclusion are more frequent than transcriptional upregulation and exon skipping upon both types of irradiation. However and most interestingly, we've identified alternative splicing events that are differentially affected by UVC and UCB, which might reflect specific CPD or 6-4 PP signaling pathways.