Study on the mechanism of LOXL1-AS1/miR-3614-5p/YY1 signal axis in the malignant phenotype regulation of hepatocellular carcinoma

Background Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with high mortality worldwide. Accumulating researches have indicated that long non‑coding RNAs (lncRNAs) are involved in varies human cancers, including HCC. Nevertheless, the specific molecular mechanism of lncRNA lysyl oxidase like 1 antisense RNA 1 (LOXL1-AS1) in HCC is still unclear. Methods LOXL1-AS1 expression was tested via qRT-PCR in HCC cells. Functional and mechanism assays were respectively done to evaluate the biological functions of HCC cells and the potential interaction of LOXL1-AS1 and other factors. Results We discovered that LOXL1-AS1 was high expressed in HCC cells. Inhibition of LOXL1-AS1 repressed cell proliferation, migration and invasion, but enhanced cell apoptosis in HCC. Further, miR-3614-5p was proven to be sponged by LOXL1-AS1. Additionally, Yin Yang 1 (YY1) was proven as the target gene of miR-3614-5p, and YY1 depletion could repress HCC cell malignant behaviors. YY1 could also transcriptionally activate LOXL1-AS1 expression. In rescue assays, we confirmed that overexpression of YY1 or miR-3614-5p inhibition could reverse the suppressive effects of LOXL1-AS1 silence on the malignant behaviors of HCC cells. Conclusion In short, LOXL1-AS1/miR-3614-5p/YY1 forms a positive loop in modulating HCC cell malignant behaviors.

Endothelial Yin Yang 1 Phosphorylation at S118 Induces Atherosclerosis Under Flow

Rationale: Disturbed flow occurring in arterial branches and curvatures induces vascular endothelial cell (EC) dysfunction and atherosclerosis. We postulated that disturbed flow plays important roles in modulating phosphoprotein expression profiles to regulate endothelial functions and atherogenesis. Objective: The goal of this study is to discover novel site-specific phosphorylation alterations induced by disturbed flow in ECs to contribute to atherosclerosis. Methods and Results: Quantitative phosphoproteomics analysis of ECs exposed to disturbed flow with low and oscillatory shear stress (OS, 0.5plusminus4 dynes/cm 2 ) vs. pulsatile flow with high shear stress (PS, 124plusminus dynes/cm 2 ) revealed that OS induces serine (S)118 phosphorylation of Yin Yang 1 (phospho-YY1 S118 ) in ECs. Elevated phospho-YY1 S118 level in ECs was further confirmed to be present in the disturbed flow regions in experimental animals and human atherosclerotic arteries. This disturbed flow-induced EC phospho-YY1 S118 is mediated by casein kinase 2α (CK2α) through its direct interaction with YY1. Yeast two-hybrid library screening and in situ proximity ligation assays demonstrate that phospho-YY1 S118 directly binds zinc finger with KRAB and SCAN domains 4 (ZKSCAN4) to induce promoter activity and gene expression of human double minute 2 (HDM2), which consequently induces EC proliferation through down-regulations of p53 and p21 CIP1 . Administration of apolipoprotein E-deficient (ApoE -/- ) mice with CK2-specific inhibitor tetrabromocinnamic acid or atorvastatin inhibits atherosclerosis formation through down-regulations of EC phospho-YY1 S118 and HDM2. Generation of novel transgenic mice bearing EC-specific overexpression of S118-non-phosphorylatable mutant of YY1 in ApoE -/- mice confirms the critical role of phospho-YY1 S118 in promoting atherosclerosis through EC HDM2. Conclusions: Our findings provide new insights into the mechanisms by which disturbed flow induces endothelial phospho-YY1 S118 to promote atherosclerosis, thus indicating phospho-YY1 S118 as a potential molecular target for atherosclerosis treatment.

YY1 lactylation in microglia promotes angiogenesis through transcription activation-mediated upregulation of FGF2

Ocular neovascularization is a leading cause of blindness. Retinal microglia have been implicated in hypoxia-induced angiogenesis and vasculopathy, but the underlying mechanisms remain largely unknown. Here, we report that lactylation in microglia is critical for retinal neovascularization. Using lactylome and proteomic analyses, we identified a list of hyperlactylated proteins in the context of increased lactate under hypoxia. Yin Yang-1 (YY1), a transcription factor, is lactylated at lysine 183 (K183) under hypoxia, which is regulated by p300. Furthermore, hyperlactylated YY1 directly enhances fibroblast growth factor 2 (FGF2) transcription and promotes angiogenesis. YY1 mutation at K183 eliminates these effects. Notably, clinical retrospective analysis shows that lactate concentrations in retinopathy of prematurity (ROP) infants are significantly increased compared with those in controls. Taken together, our results demonstrate that YY1 lactylation in microglia promotes FGF2 expression and plays a pivotal proangiogenic role, providing new insights into retinal neovascular diseases.

A histidine cluster determines YY1-compartmentalized coactivators and chromatin elements in phase-separated super-enhancers

As an oncogenic transcription factor, Yin Yang 1 (YY1) regulates enhancer and promoter connection. However, gaps still exist in understanding how YY1 coordinates coactivators and chromatin elements to assemble super-enhancers. Here, we demonstrate that YY1 activates FOXM1 gene expression through forming liquid-liquid phase separation to compartmentalize both coactivators and enhancer elements. In the transactivation domain of YY1, a histidine cluster is essential for its activities of forming phase separation, which can be extended to additional proteins. Coactivators EP300, BRD4, MED1 and active RNA polymerase II are components of YY1-rich nuclear puncta. Consistently, histone markers for gene activation, but not repression, colocalize with YY1. Importantly, multiple enhancer elements and the FOXM1 promoter are bridged by YY1 to form super-enhancers. These studies propose that YY1 is a general transcriptional activator, and promotes phase separation with incorporation of major coactivators and stabilization by distal enhancers to activate target gene expression.

FKBP51 Affects TNF-Related Apoptosis Inducing Ligand Response in Melanoma

Melanoma is one of the most immunogenic tumors and has the highest potential to elicit specific adaptive antitumor immune responses. Immune cells induce apoptosis of cancer cells either by soluble factors or by triggering cell-death pathways. Melanoma cells exploit multiple mechanisms to escape immune system tumoricidal control. FKBP51 is a relevant pro-oncogenic factor of melanoma cells supporting NF-κB-mediated resistance and cancer stemness/invasion epigenetic programs. Herein, we show that FKBP51-silencing increases TNF-related apoptosis-inducing ligand (TRAIL)-R2 (DR5) expression and sensitizes melanoma cells to TRAIL-induced apoptosis. Consistent with the general increase in histone deacetylases, as by the proteomic profile, the immune precipitation assay showed decreased acetyl-Yin Yang 1 (YY1) after FKBP51 depletion, suggesting an impaired repressor activity of this transcription factor. ChIP assay supported this hypothesis. Compared with non-silenced cells, a reduced acetyl-YY1 was found on the DR5 promoter, resulting in increased DR5 transcript levels. Using Crispr/Cas9 knockout (KO) melanoma cells, we confirmed the negative regulation of DR5 by FKBP51. We also show that KO cells displayed reduced levels of acetyl-EP300 responsible for YY1 acetylation, along with reduced acetyl-YY1. Reconstituting FKBP51 levels contrasted the effects of KO on DR5, acetyl-YY1, and acetyl-EP300 levels. In conclusion, our finding shows that FKBP51 reduces DR5 expression at the transcriptional level by promoting YY1 repressor activity. Our study supports the conclusion that targeting FKBP51 increases the expression level of DR5 and sensitivity to TRAIL-induced cell death, which can improve the tumoricidal action of immune cells.