HDAC2 phosphorylation-dependent Klf5 deacetylation and RARα acetylation induced by RAR agonist switch the transcription regulatory programs of p21 in VSMCs

Abstract

Abnormal proliferation of vascular smooth muscle cells (VSMCs) occurs in hypertension, atherosclerosis and restenosis after angioplasty, leading to pathophysiological vascular remodeling. As an important growth arrest gene, p21 plays critical roles in vascular remodeling. Regulation of p21 expression by retinoic acid receptor (RAR) and its ligand has important implications for control of pathological vascular remodeling. Nevertheless, the mechanism of RAR-mediated p21 expression in VSMCs remains poorly understood. Here, we show that, under basal conditions, RARα forms a complex with histone deacetylase 2 (HDAC2) and Krüppel-like factor 5 (Klf5) at the p21 promoter to inhibit its expression. Upon RARα agonist stimulation, HDAC2 is phosphorylated by CK2α. Phosphorylation of HDAC2, on the one hand, promotes its dissociation from RARα, thus allowing the liganded-RARα to interact with co-activators; on the other hand, it increases its interaction with Klf5, thus leading to deacetylation of Klf5. Deacetylation of Klf5 facilitates its dissociation from the p21 promoter, relieving its repressive effect on the p21 promoter. Interference with HDAC2 phosphorylation by either CK2α knockdown or the use of phosphorylation-deficient mutant of HDAC2 prevents the dissociation of Klf5 from the p21 promoter and impairs RAR agonist-induced p21 activation. Our results reveal a novel mechanism involving a phosphorylation-deacetylation cascade that functions to remove the basal repression complex from the p21 promoter upon RAR agonist treatment, allowing for optimum agonistinduced p21 expression.

Retinoic Acid Receptor α Mediates All-trans-retinoic Acid-induced Klf4 Gene Expression by Regulating Klf4 Promoter Activity in Vascular Smooth Muscle Cells

“…RAR␣ has been shown to distinctly mediate the growth inhibitory effect of retinoids and therefore is a potential target of research for preventive treatment of vascular proliferation disease (24). In VSMCs, we discovered that treatment with ATRA induced the expressions of KLF4 and RAR␣.…”

“…Although retinoid signaling is considered responsible for the direct binding of RARs/RXRs to RAREs in target gene promoters, other evidence has shown that RARs exert their effect by interacting with other general transcription factors, such as Sp1, Ets-1, cAMP response element-binding protein, and KLF5 (24,26,36,39). There are three GC boxes in the proximal region of the Klf4 promoter, which may play a vital role in Klf4 transactivation (9,18).…”

“…ATRA directly transactivates downstream target genes by binding to retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which belong to the nuclear receptor superfamily and which promote VSMC differentiation (20 -22). RARs bind to retinoic acid response elements (RAREs) and, when bound by ligands, recruit a protein complex to activate transcription (23); in the absence of ligands, RARs associate with a co-repressor complex that silences transcription (24). With other transcription factors, including Sp1/Sp3 and STAT5 (signal transducer and activator of transcription 5), RARs cooperatively transactivate the target genes (25)(26)(27).…”

miR-155-dependent regulation of mammalian sterile 20-like kinase 2 (MST2) coordinates inflammation, oxidative stress and proliferation in vascular smooth muscle cells

“…Co-immunoprecipitation was performed as described previously [24]. In brief, proteins from VSMCs were first pre-cleared with 30 μl of protein A-agarose (50% v/v).…”

Coordinating Regulation of Gene Expression in Cardiovascular Disease: Interactions between Chromatin Modifiers and Transcription Factors

“…Specifically, KLF5, retinoic acid receptor (RAR)-α, and HDAC2 interact at the p21 promoter to repress its expression and induce proliferation in VSMCs (40). When stimulated with a RAR-α agonist, HDAC2 deacetylates KLF5 to dissociate it from the p21 promoter.…”