Abstract
Atherosclerosis is one of the major cause of cardiovascular disease, which develops preferentially at arterial branches and curvatures. The fluid shear stress in these regions is oscillatory shear stress (OSS) which has been shown to play important roles in modulating various responses involved in endothelial cell (EC) dysfunction such as inflammation, proliferation, and oxidation. The other kind of fluid shear stress is pulsatile shear stress (PSS) which generally occurs in the straight part of vessels and has been shown to elicit signaling transductions to repress EC dysfunction. Therefore, fluid shear stress is considered as an important factor to modulate inflammation and the formation of atherosclerosis plaques in vascular wall. Through the phosphoproteomic analysis of OSS- and PSS-stimulated human aortic ECs (HAECs), we found that OSS induced the serine 118 phosphorylation of yin yang 1 (YY1) whereas PSS repressed the phosphorylation. Thus, we speculate that the YY1 phosphorylation (p-YY1) may contribute to the development of atherosclerosis. YY1 is known as the ubiquitous transcription factor which possesses multiple biological functions. Previous studies have demonstrated that YY1 exerted its functions by activating or repressing gene expression in response to the developmental cues or stimulations from the surrounding microenvironment. The biological functions YY1 involved include embryogenesis, cell differentiation, cell apoptosis, and tumorigenesis. Recently, it has also been reported that YY1 plays critical roles in the cardiovascular diseases. However, the roles and molecular mechanisms of endothelial YY1 in regulation of atherogenesis are still unstated. YY1 can modulate gene expression through directly acting on promoter regions or interacting with transcriptional co-activators or co-repressors to function. Thus, the aim of this study is to identify molecules which have the differential binding activity with phosphorylated YY1 mimicker (YY1S118E) and YY1 phosphorylation blocker (YY1S118A). By utilizing yeast two-hybrid screening technique which YY1S118E was used as bait and human cDNA library as prey, we identified that zinc finger with KRAB and SCAN domains 4 (ZKSCAN4) has stronger binding activity with YY1S118E. In vitro flow apparatus and cell experiment were further used to study the effect of differential flow pattern on the interaction between p-YY1 and ZKSCAN4. OSS was found to induce the association of p-YY1 and ZKSCAN4, which then activated the expression of downstream gene Hdm2 and in turn, inhibited p53 signal to facilitate the cell proliferation. Altogether, our data demonstrated that p-YY1 may involve in the development of atherosclerosis.