Regulation of Nuclear Enzymes by Phytochrome

本研究旨在确定植物色蛋白光敏色素光可逆调节核酶活性的机制，特别是染色质相关核苷三磷酸酶（NTPase）的活性。该研究旨在跟进和扩展先前的研究结果，即红光激活的光敏色素可以刺激离体豌豆细胞核的NTPase活性和核蛋白磷酸化，Ca2+和钙调蛋白在这一反应中起重要作用。将确定需要多少Ca2+来支持NTPase刺激，并确定红光是否会诱导自由ıCa2+！在核准备中。光敏色素将被免疫细胞化学定位在分离的细胞核中，以帮助评估在制备过程中它可能起作用的地方。将研究纯化的NTPase与DNA的结合。将寻找被酶识别的特定DNA序列。有证据表明NTPase可能被精胺激活的NII激酶磷酸化。该激酶将被分离和表征，以测试它是否能磷酸化NTPase，以及它的激活是否也被钙促进。所提出的实验的预期结果应该有助于提高对光和Ca2+如何调节核代谢的理解，也可能对光敏色素如何调节基因表达的模型产生影响。本项目的最终目的是了解植物光感受器光敏色素如何控制植物的生长和发育变化。目前的数据支持光敏色素在许多情况下通过诱导靶细胞膜特性的特异性改变来实现这种控制的假设。***//

This research seeks to determine the mechanisms by which the plant chromoprotein, phytochrome, photoreversibly regulates the activity of nuclear enzymes, especially that of a chromatin-associated nucleoside triphosphatase (NTPase). The research is designed to follow up and extend earlier findings which showed that red-light activated phytochrome could stimulate NTPase activity and nuclear protein phosphorylation in isolated pea nuclei and that Ca2+ and calmodulin played important roles in this response. It will be determined how much Ca2+ is required to support the NTPase stimulation and determine whether red light induces a change in the free ıCa2+! in the nuclear preparation. Phytochrome will be immunocytochemically localized in isolated nuclei to help evaluate where within the preparation it may be functioning. Binding of purified NTPase to DNA will be studied. Specific DNA sequences that are recognized by the enzyme will be sought. There is evidence the NTPase may be phosphorylated by a spermine-activated NII kinase. This kinase will be isolated and characterized to test whether it can phosphorylate the NTPase and whether its activation is promoted also by calcium.%%% Results expected from the proposed experiments should contribute significantly to an improved understanding of how light and Ca2+ can regulate nuclear metabolism, with possible implications also for models of how phytochrome regulates gene expression. The ultimate aim of this project is to understand how the plant photoreceptor, phytochrome, controls growth and development changes in plants. Current data favor the hypothesis that phytochrome achieves this control in many instances by inducing specific alterations of membrane properties in target cells.***//