Global transcriptional response after exposure of fission yeast cells to ultraviolet light

Background: In many cell types, including the fission yeast Schizosaccharomyces pombe, a set of checkpoints are induced by perturbations of the cell cycle or by DNA damage. Many of the checkpoint responses include a substantial change of the transcriptional pattern. As part of characterising a novel GI/S checkpoint in fission yeast we have investigated whether a transcriptional response is induced after irradiation with ultraviolet light. Results: Microarray analyses were used to measure the global transcription levels of all open reading frames of fission yeast after 254 nm ultraviolet irradiation, which is known to induce a GI/S checkpoint. We discovered a surprisingly weak transcriptional response, which is quite unlike the marked changes detected after some other types of treatment and in several other checkpoints. Interestingly, the alterations in gene expression after ultraviolet irradiation were not similar to those observed after ionising radiation or oxidative stress. Pathway analysis suggests that there is little systematic transcriptional response to the irradiation by ultraviolet light, but a marked, coordinated transcriptional response was noted on progression of the cells from GI to S phase. Conclusion: There is little response in fission yeast to ultraviolet light at the transcriptional level. Amongst the genes induced or repressed after ultraviolet irradiation we found none that are likely to be involved in the GI/S checkpoint mechanism, suggesting that the checkpoint is not dependent upon transcriptional regulation.