UVB-induced persistent activation of cellular pathways revealed by a loop-designed microarray approach

Ultraviolet B (UVB) irradiation has strong biological effects and modulates the expression of many genes. However, the major biological themes affected by UVB remain poorly understood. This work employs a loop-designed microarray approach and applies a log linear model along with multiple hypotheses testing to identify differentially regulated genes at 4, 8, 16, or 24 hours following UVB irradiation. The most prominent biological themes in lists of differentially regulated gene sets were extracted by functional enrichment analysis using DAVID bioinformatics resources 2007. By this approach, we identify that genes that participate in two prime cellular processes – the ribosome pathway and the oxidative phosphorylation pathway - are persistently activated over a period of 24 hours following UVB irradiation. Microarray results were further verified by both mitochondrial activity assay and real-time PCR analysis. These data suggest that the persistent activation of ribosome and oxidative phosphorylation pathways may have a key role in UVB-induced cellular responses. For the first time, the specific cellular pathways that respond to UVB irradiation consistently and persistently can be delineated confidently using a loop-designed microarray approach and functional bioinformatics analysis. The results of this study offer further insight into UVB-induced stress responses. Keywords: UVB, cDNA microarray, loop design, KEGG pathway We used a loop design in this study, cDNA microarray experiment consisted of eight RNA samples, including UVB-treated samples and their corresponding controls of 4 time points after UVB irradiation.