Induction of the transcriptional repressor Yin Yang-1 by vascular cell injury - Autocrine/paracrine role of endogenous fibroblast growth factor-2

Yin Yang-1 (YY1) is a multifunctional transcription factor that can repress the expression of many growth factor, hormone, and cytokine genes implicated in atherogenesis. YY1 expression is activated in rat vascular smooth muscle cells shortly after injury. YY1 DNA binding activity paralleled elevated protein levels in the nucleus. Smooth muscle cell injury triggered the rapid extracellular release of immunoreactive fibroblast growth factor-2 (FGF-2). YY1 induction after injury was blocked by neutralizing antibodies directed against FGF-2. This growth factor increased YY1 mRNA and protein expression and stimulated YY1 binding and transcriptional activity. Overexpression of YY1 inhibited smooth muscle cell replication. immunohistochemical analysis demonstrated YY1 staining in medial smooth muscle cells, coincident with FGF-2 expression. Proliferating cell nuclear antigen staining, in contrast, was confined mainly to the atherosclerotic intima. This is the first demonstration that YY1 is induced by either injury or FGF-2, is differentially expressed in normal and diseased human arteries, and that its overexpression inhibits vascular smooth muscle but not endothelial cell replication.