PARKER, M/E*; ADAMS, N/L; California Polytechnic State University, San Luis Obispo; California Polytechnic State University, San Luis Obispo: Effects of ultraviolet radiation on Cdc2 in Strongylocentrotus purpuratus embryos

Ultraviolet (UV) radiation has many adverse effects on cells, including delaying or inhibiting cell division. We tested whether UV radiation affects phosphorylation/activity Cdc2, a cyclin dependent kinase, which is part of the mitosis promoting factor (MPF) and which controls cell division in sea urchin embryos, Strongylocentrotus purpuratus. There are three primary phosphorylation sites that control the activity of Cdc2. Cdc2 is first phosphorylated at two inhibitory sites (tyrosine 15 (Tyr15) and threonine 14 (Thr 14)) and is subsequently phosphorylated at threonine 161 (Thr 161), an activating site. Subsequent dephosphorylation of Cdc2 at Tyr 15 allows the MPF to become active and cells to divide. Our previous results demonstrated that UVR-irradiation of eggs delays dephosphorylation of Tyr 15 (and presumably Cdc2 activity) in embryos of S. purpuratus. UV-induced delays in division of S. purpuratus(/i> are stage-dependent and embryos are more sensitive than eggs. Our current studies examined effects of UVR on Cdc2 in sea urchin embryos. Embryos were protected from or exposed to UVR that mimics the solar spectrum. Protein lysates were sparated using SDS polyacrylamide gel electrophoresis. Proteins were examined using western blotting and probed with antibodies for total Cdc2 and Cdc2 phosphorylated at Tyr 15 and Thr 161. Our results demonstrate that UVR-irradiation of early embryos causes a similar or greater delay in the dephosophorylation of Cdc2 at Tyr 15 than observed in eggs, but has no effect on activation of Thr 161.