The role of p27 on human atherosclerosis and the interplay between ROS and cell cycle control within the arterial wall will be addressed. - A) Single nucleotide polymorphisms (SNPs) within the promoter region of the p2 7 gene will be identified using DNA samples from 200 patients who survived after myocardial infarction and 200 contraols. VSMCs cultures will be transfected with plasmids in which reporter gene expression is under the controls of the p27 gene promoter containing the different SNPs. Luciferase activity of each SNP will indicate its relative transcriptional activity. To assess whether p27 SNPs are linked to increased risk of coronary disease, the frequency of each SNP will be determined in a sample of approximately 500 patients with premature heart disease and 500 healthy control individuals. Statistical analyses will be carried out to determine if altered levels of p27 due to SNPs in the promoter region of the gene are associated with increased risk of human cardiovascular disease. -B) Does oxidative stress influence atherogenesis when different levels of p27 protein are expressed? Doubly-deficient ecSOD-/- and apoE-:- mice will be generated. These mice will be mated with mice lacking p27 and the kinetics of experimental atherosclerosis after receiving a high-fat diet will be studied.