The poly(ADP-ribosyl)ation of BRD4 mediated by PARP1 promoted pathological cardiac hypertrophy

Abstract

The bromodomain and extraterminal (BET) family member BRD4 is pivotal in the pathogenesis of cardiac hypertrophy. BRD4 induces hypertrophic gene expression by binding to the acetylated chromatin, facilitating the phosphorylation of RNA polymerases II (Pol II) and leading to transcription elongation. The present study identified a novel post-translational modification of BRD4: poly(ADP-ribosyl)ation (PARylation), that was mediated by poly(ADP-ribose)polymerase-1 (PARP1) in cardiac hypertrophy. BRD4 silencing or BET inhibitors JQ1 and MS417 prevented cardiac hypertrophic responses induced by isoproterenol (ISO), whereas overexpression of BRD4 promoted cardiac hypertrophy, confirming the critical role of BRD4 in pathological cardiac hypertrophy. PARP1 was activated in ISO-induced cardiac hypertrophy and facilitated the development of cardiac hypertrophy. BRD4 was involved in the prohypertrophic effect of PARP1, as implied by the observations that BRD4 inhibition or silencing reversed PARP1-induced hypertrophic responses, and that BRD4 overexpression suppressed the anti-hypertrophic effect of PARP1 inhibitors. Interactions of BRD4 and PARP1 were observed by co-immunoprecipitation and immunofluorescence. PARylation of BRD4 induced by PARP1 was investigated by PARylation assays. In response to hypertrophic stimuli like ISO, PARylation level of BRD4 was elevated, along with enhanced interactions between BRD4 and PARP1. By investigating the PARylation of truncation mutants of BRD4, the C-terminal domain (CTD) was identified as the PARylation modification sites of BRD4. PARylation of BRD4 facilitated its binding to the transcription start sites (TSS) of hypertrophic genes, resulting in enhanced phosphorylation of RNA Pol II and transcription activation of hypertrophic genes. The present findings suggest that strategies targeting inhibition of PARP1-BRD4 might have therapeutic potential for pathological cardiac hypertrophy.

Tripartite motif 27 promotes cardiac hypertrophy via PTEN/Akt/mTOR signal pathways

“…The formalin-embedded hearts were sliced into 6 μm sections that were stained with hematoxylin and eosin (H&E) using wheat germ agglutinin (WGA) to quantify CH and picrosirius red (PSR) to quantify cardiac fibrosis [ 25 ].…”

RNA polymerase II and PARP1 shape enhancer-promoter contacts

“…The effect of paused Pol II highlighted another protein known to be involved in interactions between transcriptionrelated proteins, PARP1, as a potential regulator of enhancer-promoter contacts. PARP1 is an enzyme which catalyzes the formation of poly (ADP-ribose) (PAR) chains, a post-translational modification added to transcription and chromatin-associated proteins (which are said to be "PARylated") near active enhancer and promoter regions (55)(56)(57)(58)(59)(60)(61). PAR chains play a critical role in driving the formation of molecular clusters through interactions with intrinsically disordered regions (IDRs) of proteins (62).…”

Epigenetic Reader Bromodomain Containing Protein 2 Facilitates Pathological Cardiac Hypertrophy via Regulating the Expression of Citrate Cycle Genes

“…Notably, BRD2 shares close similarity in structure and physiological role with BRD4 ( Devaiah et al, 2016 ), which is well-accepted to be a nodal regulator of cardiac hypertrophy ( Van der Feen et al, 2019 ; Zhu et al, 2020 ; Li et al, 2021 ). However, BRD4 possesses a longer CTD with a unique function that could facilitate the recruitment of P-TEFb complex to promote transcriptional elongation of hypertrophic genes, finally contributing to cardiac hypertrophy ( Belkina and Denis 2012 ; Spiltoir et al, 2013 ).…”

“…Another BETi, apabetalone (RVX-208), improves the cardiovascular outcomes of patients with diabetes after acute coronary syndrome, suggesting its therapeutic potential for cardiovascular diseases ( Ray et al, 2019 ). Among the four BET family members, BRD4 has been widely reported to be involved in regulation of cardiac hypertrophy ( Van der Feen et al, 2019 ; Zhu et al, 2020 ; Li et al, 2021 ). However, the roles of other BET members in pathological cardiac hypertrophy remain unclear.…”

“…In our preliminary studies, we measured the mRNA levels of BET members in a cardiomyocyte hypertrophy model induced by β-adrenergic receptor activation. BRD2 was remarkably elevated at the transcriptional level in parallel with BRD4, suggesting that BRD2 is probably associated with the pathological progression of cardiac hypertrophy ( Li et al, 2021 ).…”