UV-B activates the transcriptional expression of Pl-c-jun, an early responsive gene in sea urchin embryos.

UV-B activates the transcriptional expression of Pl-c-jun, an early responsive gene in sea urchin embryos. R. Russo, R. Bonaventura, F. Zito, A. Pinsino and V. Matranga Consiglio Nazionale delle Ricerche, Istituto di Biomedicina e Immunologia Molecolare, "Alberto Monroy", Via Ugo La Malfa 153, 90146 Palermo, Italy Abstract UV-B is a harmful radiation that reaches the Earth's surface and causes damages in all organisms by inducing oxidative stress, thus altering biochemical and physiological functioning of cellular targets, DNA or proteins. UV-B can have severe physiological consequences on marine organisms such as sea urchins. One of the proteins responsive to UV-B stress is AP-1, a transcription factor involved in many important cellular events such as cell cycle regulation, cell proliferation and differentiation.AP-1 is a heterodimeric protein, composed by the association of different proteins, including c-jun, junB, c-fos, Fra-1 and Fra-2, that takes part to the cell signaling network, being a specific target of JNK kinase. Here, we describe the isolation of the complete cDNA encoding for Pl-c-jun from Paracentrotus lividus sea urchin embryos and the phylogenetic relationships with other homologs described in different phyla. Pl-c-jun mRNA levels were measured by Quantitative Polymerase Chain Reaction during development. In response to UV-B exposure at 400 and 800 J/m2, early stage embryos (32 cells) collected two hours later showed a great increase in Pl-c-jun transcript levels compared to controls. The spatial expression of Pl-c-jun mRNA was detected by Whole Mount In Situ Hybridization in control and UV-B exposed embryos. In control embryos transcripts were found in the vegetative region at blastula stage and in the Primary Mesenchyme Cells (PMC) at gastrula and pluteus stages, while in UV-B exposed embryos, at late developmental stages (gastrula and pluteus), the mRNA was ectopically expressed. The Pl-c-jun phospho-protein was detected by immunohystochemistry on whole mount embryos and its nuclear localization in PMC cells was confirmed. Pl-c-jun up-regulation in response to UV-B stress suggests that, in P.lividus embryos, it is able to trigger an early cascade of transcriptional events to protect embryos from UV-B damage, maybe through the ROS-JNK pathway activation.