PDGF-BB-mediated activation of CREB in vascular smooth muscle cells alters cell cycling via Rb, FoxO1 and p27kip1

Dynamic deployment of H2A.Z positive nucleosome mediated transcriptomic plasticity within vascular smooth muscle cell

BACKGROUND

To maintain homeostasis in the mature human body, certain differentiated cells adopted high plasticity to refine their cellular functions. However, mechanisms that supported cellular plasticity still remained elusive. Here, through comprehensive transcriptomic and epigenetic studies of highly plastic vascular smooth muscle cells (SMCs), we aimed to decipher the chromatin basis that could mediate cellular plasticity.

RESULTS

In vascular smooth muscle cells, actively transcribed and highly adjustable genes tended to be associated with a continuously accessible region downstream of transcription start site (CAR-downTSS). This CAR-downTSS was located beyond the classic RNA polymerase II paused region, accessible at mono-nucleosome level and incorporated with histone variant H2A.Z. Depletion of H2A.Z reduced active histone modifications within CAR-downTSS, impaired RNA polymerase II transpassing when cells were stimulated, and consequently inhibited the ability of CAR-downTSS-associated genes to adjust their expression. Further in vitro and in vivo studies verified that this CAR-downTSS could be dynamically re-deployed onto different genes in vascular SMCs, whereas it was deployed in smaller quantities and remained quantitatively stable on genome within the quiescent cardiomyocytes.

CONCLUSIONS

Vascular SMCs dynamically deployed H2A.Z-positive nucleosomes extending continuously downstream transcription start sites on different genes to support their transcriptional adjustability, which served as an important mechanism mediating cellular plasticity.

Nitration of cAMP-Response Element Binding Protein Participates in Myocardial Infarction-Induced Myocardial Fibrosis via Accelerating Transcription of Col1a2 and Cxcl12

Aims: Myocardial fibrosis after myocardial infarction (MI) leads to heart failure. Nitration of protein can alter its function. cAMP-response element binding protein (CREB) is a key transcription factor involved in fibrosis. However, little is known about the role of nitrated CREB in MI-induced myocardial fibrosis. Meanwhile, downstream genes of transcription factor CREB in myocardial fibrosis have not been identified. This study aims to verify the hypothesis that nitrated CREB promotes MI-induced myocardial fibrosis via regulating the transcription of Col1a2 and Cxcl12. Results: Our study showed that (1) the level of nitrative stress was elevated and nitrated CREB was higher in the myocardium after MI. Tyr182, 307, and 336 were the nitration sites of CREB; (2) with the administration of peroxynitrite (ONOO^-) scavengers, CREB phosphorylation, nuclear translocation, and binding activity to TORC2 (transducers of regulated CREB-2) were attenuated; (3) the expressions of extracellular matrix (ECM) proteins were upregulated and downregulated in accordance with the expression alteration of CREB both in vitro and in vivo; (4) CREB accelerated transcription of Col1a2 and Cxcl12 after MI directly. With the administration of ONOO^- scavengers, ECM protein expressions were attenuated; meanwhile, the messenger RNA (mRNA) levels of Col1a2 and Cxcl12 were alleviated as well. Innovation and Conclusion: Nitration of transcription factor CREB participates in MI-induced myocardial fibrosis through enhancing its phosphorylation, nuclear translocation, and binding activity to TORCs, among which CREB transcripts Col1a2 and Cxcl12 directly. These data indicated that nitrated CREB might be a potential therapeutic target against MI-induced myocardial fibrosis.