Phase separation of PML/RARα and BRD4 coassembled microspeckles governs transcriptional dysregulation in acute promyelocytic leukemia.

In acute promyelocytic leukemia (APL), the promyelocytic leukemia-retinoic acid receptor alpha (PML/RARα) fusion protein destroys PML nuclear bodies (NBs), leading to the formation of microspeckles. However, our understanding, largely learned from morphological observations, lacks insight into the mechanisms behind PML/RARα-mediated microspeckle formation and its role in APL leukemogenesis. This study presents evidence uncovering liquid-liquid phase separation (LLPS) as a key mechanism in the formation of PML/RARα-mediated microspeckles. This process is facilitated by the intrinsically disordered region containing a large portion of PML and a smaller segment of RARα. We demonstrate the coassembly of bromodomain-containing protein 4 (BRD4) within PML/RARα-mediated condensates, differing from wild-type PML-formed NBs. In the absence of PML/RARα, PML NBs and BRD4 puncta exist as two independent phases, but the presence of PML/RARα disrupts PML NBs and redistributes PML and BRD4 into a distinct phase, forming PML/RARα-assembled microspeckles. Genome-wide profiling reveals a PML/RARα-induced BRD4 redistribution across the genome, with preferential binding to super-enhancers and broad-promoters (SEBPs). Mechanistically, BRD4 is recruited by PML/RARα into nuclear condensates, facilitating BRD4 chromatin binding to exert transcriptional activation essential for APL survival. Perturbing LLPS through chemical inhibition (1, 6-hexanediol) significantly reduces chromatin co-occupancy of PML/RARα and BRD4, attenuating their target gene activation. Finally, a series of experimental validations in primary APL patient samples confirm that PML/RARα forms microspeckles through condensates, recruits BRD4 to coassemble condensates, and co-occupies SEBP regions. Our findings elucidate the biophysical, pathological, and transcriptional dynamics of PML/RARα-assembled microspeckles, underscoring the importance of BRD4 in mediating transcriptional activation that enables PML/RARα to initiate APL.

ATRA regulates myoblast differentiation and fusion through the RARα/Pitx2 signaling pathway, causing abnormal development of PFMs in ARM fetal rats.

Anorectal malformation (ARM) is the most common congenital digestive tract anomaly in newborns, and children with ARM often have varying degrees of underdevelopment of the pelvic floor muscles (PFMs). To explore the effects of RARα and Pitx2 on the development of rat PFMs, we constructed a rat ARM animal model using all-trans retinoic acid (ATRA), and verified the expression of RARα and Pitx2 in the PFMs of fetal rats. Additionally, we used rat myoblasts (L6 cells) to investigate the regulatory roles of RARα and Pitx2 in skeletal muscle myoblast differentiation and their interactions. The results indicated a significant decrease in the expression of RARα and Pitx2 in the PFMs of fetal rats with ARM. ATRA can also decrease the expression of RARα and Pitx2 in the L6 cells, while affecting the differentiation and fusion of L6 cells. Knocking down RARα in L6 cells reduced the expression of Pitx2, MYOD1, MYMK, and decreased myogenic activity in L6 cells. When RARα is activated, the decreased expression of Pitx2, MYOD1, and MYMK and myogenic differentiation can be restored to different extents. At the same time, increasing or inhibiting the expression of Pitx2 can counteract the effects of knocking down RARα and activating RARα respectively. These results indicate that Pitx2 may be downstream of the transcription factor RARα, mediating the effects of ATRA on the development of fetal rat PFMs.

Decoding the neurotoxic effects of propofol: insights into the RARα-Snhg1-Bdnf regulatory cascade.

The potential neurotoxic effects of propofol, an extensively utilized anesthetic, underline the urgency to comprehend its influence on neuronal health. Insights into the role of the retinoic acid receptor-α, small nucleolar RNA host gene 1, and brain-derived neurotrophic factor (RARα-Snhg1-Bdnf) network can offer significant advancements in minimizing these effects. The study targets the exploration of the RARα and Snhg1 regulatory network's influence on Bdnf expression in the realm of propofol-induced neurotoxicity. Harnessing the Gene Expression Omnibus (GEO) database and utilizing JASPAR and RNA-Protein Interaction Prediction (RPISeq) database for projections, the study embarks on an in-depth analysis employing both in vitro and in vivo models. The findings draw a clear link between propofol-induced neurotoxicity and the amplification of RAR signaling pathways, impacting hippocampal development and apoptosis and leading to increased RARα and Snhg1 and decreased Bdnf. Propofol is inferred to accentuate neurotoxicity by heightening RARα and Snhg1 interactions, culminating in Bdnf suppression.NEW & NOTEWORTHY This study aimed to decode propofol's neurotoxic effects on the regulatory cascade, provide insights into the RARα-Snhg1-Bdnf interaction, apply extensive validation techniques, provide a detailed analysis and exploration of propofol's neurotoxicity, and offer a comprehensive approach to understanding molecular interactions.

Agonist-controlled competition of RAR and VDR nuclear receptors for heterodimerization with RXR is manifested in their DNA binding.

We found previously that nuclear receptors (NRs) compete for heterodimerization with their common partner, retinoid X receptor (RXR), in a ligand-dependent manner. To investigate potential competition in their DNA binding, we monitored the mobility of retinoic acid receptor (RAR) and vitamin D receptor (VDR) in live cells by fluorescence correlation spectroscopy. First, specific agonist treatment and RXR coexpression additively increased RAR DNA binding, while both agonist and RXR were required for increased VDR DNA binding, indicating weaker DNA binding of the VDR/RXR dimer. Second, coexpression of RAR, VDR, and RXR resulted in competition for DNA binding. Without ligand, VDR reduced the DNA-bound fraction of RAR and vice versa, i.e., a fraction of RXR molecules was occupied by the competing partner. The DNA-bound fraction of either RAR or VDR was enhanced by its own and diminished by the competing NR's agonist. When treated with both ligands, the DNA-bound fraction of RAR increased as much as due to its own agonist, whereas that of VDR increased less. RXR agonist also increased DNA binding of RAR at the expense of VDR. In summary, competition between RAR and VDR for RXR is also manifested in their DNA binding in an agonist-dependent manner: RAR dominates over VDR in the absence of agonist or with both agonists present. Thus, side effects of NR-ligand-based (retinoids, thiazolidinediones) therapies may be ameliorated by other NR ligands and be at least partly explained by reduced DNA binding due to competition. Our results also complement the model of NR action by involving competition both for RXR and for DNA sites.

Energy status regulates levels of the RAR/RXR ligand 9-cis-retinoic acid in mammalian tissues: Glucose reduces its synthesis in ß-cells.

9-cis-retinoic acid (9cRA) binds retinoic acid receptors (RAR) and retinoid X receptors (RXR) with nanomolar affinities, in contrast to all-trans-retinoic acid (atRA), which binds only RAR with nanomolar affinities. RXR heterodimerize with type II nuclear receptors, including RAR, to regulate a vast gene array. Despite much effort, 9cRA has not been identified as an endogenous retinoid, other than in pancreas. By revising tissue analysis methods, 9cRA quantification by liquid chromatography-tandem mass spectrometry becomes possible in all mouse tissues analyzed. 9cRA occurs in concentrations similar to or greater than atRA. Fasting increases 9cRA in white and brown adipose, brain and pancreas, while increasing atRA in white adipose, liver and pancreas. 9cRA supports FoxO1 actions in pancreas ß-cells and counteracts glucose actions that lead to glucotoxicity; in part by inducing Atg7 mRNA, which encodes the key enzyme essential for autophagy. Glucose suppresses 9cRA biosynthesis in the ß-cell lines 832/13 and MIN6. Glucose reduces 9cRA biosynthesis in 832/13 cells by inhibiting Rdh5 transcription, unconnected to insulin, through cAMP and Akt, and inhibiting FoxO1. Through adapting tissue specifically to fasting, 9cRA would act independent of atRA. Widespread occurrence of 9cRA in vivo, and its self-sufficient adaptation to energy status, provides new perspectives into regulation of energy balance, attenuation of insulin and glucose actions, regulation of type II nuclear receptors, and retinoid biology.

Insufficient support for retinoic acid receptor control of synaptic plasticity through a non-genomic mechanism.

It is well established that retinoic acid receptors (RARs) function as nuclear receptors that control gene expression in response to binding of the ligand retinoic acid (RA). However, some studies have proposed that RAR-alpha (RARa) controls synaptic plasticity via non-genomic effects outside the nucleus, i.e. effects on mRNA translation of GluA1, a sub-unit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. In order to support this non-genomic mechanism, studies have reported RARa knockout mice or treatment with pharmacological levels of RA and RAR antagonists to propose that RARa is required to control normal synaptic plasticity. A major shortcoming of the non-genomic hypothesis is that there have been no mutational studies showing that RARa can bind the GluA1 mRNA to control GLUA1 protein levels in a non-genomic manner. Also, without a genetic study that removes the endogenous ligand RA, it is impossible to conclude that RARa and its ligand RA control synaptic plasticity through a non-genomic signaling mechanism.

Nuclear receptors for epidermal lipid barrier: Advances in mechanisms and applications.

The skin plays an essential role in preventing the entry of external environmental threats and the loss of internal substances, depending on the epidermal permeability barrier. Nuclear receptors (NRs), present in various tissues and organs including full-thickness skin, have been demonstrated to exert significant effects on the epidermal lipid barrier. Formation of the lipid lamellar membrane and the normal proliferation and differentiation of keratinocytes (KCs) are crucial for the development of the epidermal permeability barrier and is regulated by specific NRs such as PPAR, LXR, VDR, RAR/RXR, AHR, PXR and FXR. These receptors play a key role in regulating KC differentiation and the entire process of epidermal lipid synthesis, processing and secretion. Lipids derived from sebaceous glands are influenced by NRs as well and participate in regulation of the epidermal lipid barrier. Furthermore, intricate interplay exists between these receptors. Disturbance of barrier function leads to a range of diseases, including psoriasis, atopic dermatitis and acne. Targeting these NRs with agonists or antagonists modulate pathways involved in lipid synthesis and cell differentiation, suggesting potential therapeutic approaches for dermatosis associated with barrier damage. This review focuses on the regulatory role of NRs in the maintenance and processing of the epidermal lipid barrier through their effects on skin lipid synthesis and KC differentiation, providing novel insights for drug targets to facilitate precision medicine strategies.

Long-term results and quality of life after stapled hemorrhoidopexy vs Doppler-guided HAL-RAR: a propensity score matching analysis.

AIM: The study aimed to evaluate and compare the short and long-term outcomes of doppler-guided (DG) hemorrhoidal artery ligation and rectoanal repair (HAL-RAR) using a wireless-doppler-guided probe and stapled hemorrhoidopexy (SH) for treatment of II-III hemorrhoids. METHODS: This cohort study included patients who underwent HAL-RAR (n = 89) or SH (n = 174) for grade II-III hemorrhoids between January 2020 and December 2021. After propensity score matching at a 1:1 ratio, 76 patients for each group were analyzed. Short and long-term outcomes were collected. Pain was measured using a Visual Analogue Scale (VAS) at POD1, POD 10, 1 month, and 6 months after surgery. The enrolled patients completed the Hemorrhoidal Disease Symptom Score and Short Health ScaleHD quality of life (HDSS/SHS QoL) questionnaire preoperatively and during a regular follow-up visit at 24 months after surgery. RESULTS: Groups exhibited comparable overall postoperative complication rates (23% HAL-RAR/ 21% SH; p = 0.295). Postoperative pain via VAS showed median scores of 4, 3, 1, 1 for HAL-RAR and 6, 4, 2, 1 for SH at POD1, POD10, 1 month, and 6 months, respectively (p = < 0.001, 0.004, 0.025, 0.019). At a median follow-up of 12 months, the recurrence rate was 10.5% in the HAL-RAR group and 9.2% in the SH group (p = 0.785), respectively. At 24 months, 15.7% of HAL-RAR patients and 19.7% of SH patients remained symptomatic (p = 0.223). Median post-op QoL index was 1 (HAL-RAR) and 0.92 (SH), p = 0.036. CONCLUSIONS: HAL-RAR is a safe and feasible technique in treating grade II-III hemorrhoids showing better outcomes in terms of postoperative pain and QoL. SIGNIFICANCE: This paper adds a new perspective in comparing the HAL-RAR and SH, focusing the attention on the patients and not surgical techniques. A long and difficult follow-up was completed to fully understand the long-term results and the impact on the QoL of the patients who underwent these procedures.

Targeting AFP-RARß complex formation: a potential strategy for treating AFP-positive hepatocellular carcinoma.

Alpha-fetoprotein (AFP) is a glycoprotein primarily expressed during embryogenesis, with declining levels postnatally. Elevated AFP levels correlate with pathological conditions such as liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Recent investigations underscore AFP's intracellular role in HCC progression, wherein it forms complexes with proteins like Phosphatase and tensin homolog (PTEN), Caspase 3 (CASP3), and Retinoic acid receptors and Retinoid X receptors (RAR/RXR). RAR and RXR regulate gene expression linked to cell death and tumorigenesis in normal physiology. AFP impedes RAR/RXR dimerization, nuclear translocation, and function, promoting gene expression favoring cancer progression in HCC that provoked us to target AFP as a drug candidate. Despite extensive studies, inhibitors targeting AFP to disrupt complex formation and activities remain scarce. In this study, employing protein-protein docking, amino acid residues involved in AFP-RARß interaction were identified, guiding the definition of AFP's active site for potential inhibitor screening. Currently, kinase inhibitors play a significant role in cancer treatment and, the present study explores the potential of repurposing FDA-approved protein kinase inhibitors to target AFP. Molecular docking with kinase inhibitors revealed Lapatinib as a candidate drug of the AFP-RARß complex. Molecular dynamics simulations and binding energy calculations, employing Mechanic/Poisson-Boltzmann Surface Area (MM-PBSA), confirmed Lapatinib's stability with AFP. The study suggests Lapatinib's potential in disrupting the AFP-RARß complex, providing a promising avenue for treating molecularly stratified AFP-positive HCC or its early stages.

OCT4 Acts as an Integrator of Pluripotency and Signal-Induced Differentiation.

Cell type specification relies on the capacity of undifferentiated cells to properly respond to specific differentiation-inducing signals. Using genomic approaches along with loss- and gain-of-function genetic models, we identified OCT4-dependent mechanisms that provide embryonic stem cells with the means to customize their response to external cues. OCT4 binds a large set of low-accessible genomic regions. At these sites, OCT4 is required for proper enhancer and gene activation by recruiting co-regulators and RAR:RXR or ß-catenin, suggesting an unexpected collaboration between the lineage-determining transcription factor and these differentiation-initiating, signal-dependent transcription factors. As a proof of concept, we demonstrate that overexpression of OCT4 in a kidney cell line is sufficient for signal-dependent activation of otherwise unresponsive genes in these cells. Our results uncover OCT4 as an integral and necessary component of signal-regulated transcriptional processes required for tissue-specific responses.

Identification of a KLF5-dependent program and drug development for skeletal muscle atrophy.

Skeletal muscle atrophy is caused by various conditions, including aging, disuse related to a sedentary lifestyle and lack of physical activity, and cachexia. Our insufficient understanding of the molecular mechanism underlying muscle atrophy limits the targets for the development of effective pharmacologic treatments and preventions. Here, we identified Krüppel-like factor 5 (KLF5), a zinc-finger transcription factor, as a key mediator of the early muscle atrophy program. KLF5 was up-regulated in atrophying myotubes as an early response to dexamethasone or simulated microgravity in vitro. Skeletal muscle-selective deletion of Klf5 significantly attenuated muscle atrophy induced by mechanical unloading in mice. Transcriptome- and genome-wide chromatin accessibility analyses revealed that KLF5 regulates atrophy-related programs, including metabolic changes and E3-ubiquitin ligase-mediated proteolysis, in coordination with Foxo1. The synthetic retinoic acid receptor agonist Am80, a KLF5 inhibitor, suppressed both dexamethasone- and microgravity-induced muscle atrophy in vitro and oral Am80 ameliorated disuse- and dexamethasone-induced atrophy in mice. Moreover, in three independent sets of transcriptomic data from human skeletal muscle, KLF5 expression significantly increased with age and the presence of sarcopenia and correlated positively with the expression of the atrophy-related ubiquitin ligase genes FBXO32 and TRIM63 These findings demonstrate that KLF5 is a key transcriptional regulator mediating muscle atrophy and that pharmacological intervention with Am80 is a potentially preventive treatment.

RAR Inhibitors Display Photo-Protective and Anti-Inflammatory Effects in A2E Stimulated RPE Cells In Vitro through Non-Specific Modulation of PPAR or RXR Transactivation.

N-retinylidene-N-retinylethanolamine (A2E) has been associated with age-related macular degeneration (AMD) physiopathology by inducing cell death, angiogenesis and inflammation in retinal pigmented epithelial (RPE) cells. It was previously thought that the A2E effects were solely mediated via the retinoic acid receptor (RAR)-α activation. However, this conclusion was based on experiments using the RAR "specific" antagonist RO-41-5253, which was found to also be a ligand and partial agonist of the peroxisome proliferator-activated receptor (PPAR)-γ. Moreover, we previously reported that inhibiting PPAR and retinoid X receptor (RXR) transactivation with norbixin also modulated inflammation and angiogenesis in RPE cells challenged in the presence of A2E. Here, using several RAR inhibitors, we deciphered the respective roles of RAR, PPAR and RXR transactivations in an in vitro model of AMD. We showed that BMS 195614 (a selective RAR-α antagonist) displayed photoprotective properties against toxic blue light exposure in the presence of A2E. BMS 195614 also significantly reduced the AP-1 transactivation and mRNA expression of the inflammatory interleukin (IL)-6 and vascular endothelial growth factor (VEGF) induced by A2E in RPE cells in vitro, suggesting a major role of RAR in these processes. Surprisingly, however, we showed that (1) Norbixin increased the RAR transactivation and (2) AGN 193109 (a high affinity pan-RAR antagonist) and BMS 493 (a pan-RAR inverse agonist), which are photoprotective against toxic blue light exposure in the presence of A2E, also inhibited PPARs transactivation and RXR transactivation, respectively. Therefore, in our in vitro model of AMD, several commercialized RAR inhibitors appear to be non-specific, and we propose that the phototoxicity and expression of IL-6 and VEGF induced by A2E in RPE cells operates through the activation of PPAR or RXR rather than by RAR transactivation.

Activity-dependent modulation of neuronal KV channels by retinoic acid enhances CaV channel activity.

The metabolite of vitamin A, retinoic acid (RA), is known to affect synaptic plasticity in the nervous system and to play an important role in learning and memory. A ubiquitous mechanism by which neuronal plasticity develops in the nervous system is through modulation of voltage-gated Ca2+ (CaV) and voltage-gated K+ channels. However, how retinoids might regulate the activity of these channels has not been determined. Here, we show that RA modulates neuronal firing by inducing spike broadening and complex spiking in a dose-dependent manner in peptidergic and dopaminergic cell types. Using patch-clamp electrophysiology, we show that RA-induced complex spiking is activity dependent and involves enhanced inactivation of delayed rectifier voltage-gated K+ channels. The prolonged depolarizations observed during RA-modulated spiking lead to an increase in Ca2+ influx through CaV channels, though we also show an opposing effect of RA on the same neurons to inhibit Ca2+ influx. At physiological levels of Ca2+, this inhibition is specific to CaV2 (not CaV1) channels. Examining the interaction between the spike-modulating effects of RA and its inhibition of CaV channels, we found that inhibition of CaV2 channels limits the Ca2+ influx resulting from spike modulation. Our data thus provide novel evidence to suggest that retinoid signaling affects both delayed rectifier K+ channels and CaV channels to fine-tune Ca2+ influx through CaV2 channels. As these channels play important roles in synaptic function, we propose that these modulatory effects of retinoids likely contribute to synaptic plasticity in the nervous system.

A stripe rust fungal effector PstSIE1 targets TaSGT1 to facilitate pathogen infection.

Puccinia striiformis f. sp. tritici (Pst), the causal agent of stripe rust, is a destructive pathogen of Triticum aestivum (wheat), threatening wheat production worldwide. Pst delivers hundreds of effectors to manipulate processes in its hosts during infection. The SGT1 (suppressor of the G2 allele of skp1), RAR1 (required for Mla12 resistance) and HSP90 (heat-shock protein 90) proteins form a chaperone complex that acts as a core modulator in plant immunity. However, little is known about how Pst effectors target this immune component to suppress plant immunity. Here, we identified a Pst effector PstSIE1 that interacts with TaSGT1 in wheat and is upregulated during the early infection stage. Transient expression of PstSIE1 suppressed cell death in Nicotiana benthamiana induced by VmE02 and PcNLP2. Transgenic expression of PstSIE1-RNAi constructs in wheat significantly reduced the virulence of Pst. Overexpression of PstSIE1 in wheat increased the number of rust pustules and reduced the accumulation of reactive oxygen species (ROS), indicating that PstSIE1 functions as an important pathogenicity factor in Pst. PstSIE1 was found to compete with TaRAR1 to bind TaSGT1, thus disrupting the formation of the TaRAR1-TaSGT1 subcomplex. Taken together, PstSIE1 is an important Pst effector targeting the immune component TaSGT1 and involved in suppressing wheat defense.

Bone marrow overexpression of SNAI1 is an early indicator of intrinsic drug resistance in patients with de novo acute myeloid leukemia.

BACKGROUND: The lack of effectiveness of acute myeloid leukemia (AML) treatment remains a major challenge and resembles a principal cause of AML-related mortality owing to chemotherapy resistance. SNAI1 has been proved to be a leading factor in drug resistance in many cancer types. However, its relation to chemoresistance in AML is not well understood. METHODS: In addition to standard lab work, the expression level of SNAI1 was determined in bone marrow samples of 109 adult and pediatric patients with de novo acute myeloid leukemia using RT-qPCR. The relation between SNAI1 and AML drug resistance and immunomodulatory genes was investigated using the STRING tool. RESULTS: The SNAI1 expression level was upregulated in AML patients in particular samples with promyelocytic leukemia subtype against control cases. In the treatment response, SNAI1 was significantly higher in resistant patients in comparison with the complete remission group. SNAI1 overexpression was associated with high initial blasts and total leukocyte counts, but with HLA class II histocompatibility antigen DR downregulation. STRING analysis showed that multiple drug resistance and immunomodulatory genes of AML induce SNAI upregulation and activation. Kaplan-Meier analysis indicated that there was no relation between SNAI1 expression level and patient survival status. CONCLUSION: We conclude that the SNAI1 expression level may be a predictor of intrinsic drug resistance incidence in AML patients.

Urine Excretion, Organ Distribution, and Placental Transfer of 6PPD and 6PPD-Quinone in Mice and Potential Developmental Toxicity through Nuclear Receptor Pathways.

The rubber antioxidant 6PPD has gained significant attention due to its highly toxic transformation product, 6PPD-quinone (6PPDQ). Despite their detection in urines of pregnant women, the placental transfer and developmental toxicity of 6PPD and 6PPDQ are unknown. Here, we treated C57Bl/6 mice with 4 mg/kg 6PPD or 6PPDQ to investigate their urine excretion and placental transfer. Female and male mice exhibited sex difference in excretion profiles of 6PPD and 6PPDQ. Urine concentrations of 6PPDQ were one order of magnitude lower than those of 6PPD, suggesting lower excretion and higher bioaccumulation of 6PPDQ. In pregnant mice treated with 6PPD or 6PPDQ from embryonic day 11.5 to 15.5, 6PPDQ showed ∼1.5-8 times higher concentrations than 6PPD in placenta, embryo body, and embryo brain, suggesting higher placental transfer of 6PPDQ. Using in vitro dual-luciferase reporter assays, we revealed that 6PPDQ activated the human retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) at concentrations as low as 0.3 µM, which was ∼10-fold higher than the concentrations detected in human urines. 6PPD activated the RXRα at concentrations as low as 1.2 µM. These results demonstrate the exposure risks of 6PPD and 6PPDQ during pregnancy and emphasize the need for further toxicological and epidemiological investigations.

Hyperthermia promotes degradation of the acute promyelocytic leukemia driver oncoprotein ZBTB16/RARα.

The acute promyelocytic leukemia (APL) driver ZBTB16/RARα is generated by the t(11;17) (q23;q21) chromosomal translocation, which is resistant to combined treatment of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) or conventional chemotherapy, resulting in extremely low survival rates. In the current study, we investigated the effects of hyperthermia on the oncogenic fusion ZBTB16/RARα protein to explore a potential therapeutic approach for this variant APL. We showed that Z/R fusion protein expressed in HeLa cells was resistant to ATO, ATRA, and conventional chemotherapeutic agents. However, mild hyperthermia (42 °C) rapidly destabilized the ZBTB16/RARα fusion protein expressed in HeLa, 293T, and OCI-AML3 cells, followed by robust ubiquitination and proteasomal degradation. In contrast, hyperthermia did not affect the normal (i.e., unfused) ZBTB16 and RARα proteins, suggesting a specific thermal sensitivity of the ZBTB16/RARα fusion protein. Importantly, we found that the destabilization of ZBTB16/RARα was the initial step for oncogenic fusion protein degradation by hyperthermia, which could be blocked by deletion of nuclear receptor corepressor (NCoR) binding sites or knockdown of NCoRs. Furthermore, SIAH2 was identified as the E3 ligase participating in hyperthermia-induced ubiquitination of ZBTB16/RARα. In short, these results demonstrate that hyperthermia could effectively destabilize and subsequently degrade the ZBTB16/RARα fusion protein in an NCoR-dependent manner, suggesting a thermal-based therapeutic strategy that may improve the outcome in refractory ZBTB16/RARα-driven APL patients in the clinic.

Revisiting APP secretases: an overview on the holistic effects of retinoic acid receptor stimulation in APP processing.

Alzheimer's disease (AD) is the leading cause of dementia worldwide and is characterized by the accumulation of the ß-amyloid peptide (Aß) in the brain, along with profound alterations in phosphorylation-related events and regulatory pathways. The production of the neurotoxic Aß peptide via amyloid precursor protein (APP) proteolysis is a crucial step in AD development. APP is highly expressed in the brain and is complexly metabolized by a series of sequential secretases, commonly denoted the α-, ß-, and γ-cleavages. The toxicity of resulting fragments is a direct consequence of the first cleaving event. ß-secretase (BACE1) induces amyloidogenic cleavages, while α-secretases (ADAM10 and ADAM17) result in less pathological peptides. Hence this first cleavage event is a prime therapeutic target for preventing or reverting initial biochemical events involved in AD. The subsequent cleavage by γ-secretase has a reduced impact on Aß formation but affects the peptides' aggregating capacity. An array of therapeutic strategies are being explored, among them targeting Retinoic Acid (RA) signalling, which has long been associated with neuronal health. Additionally, several studies have described altered RA levels in AD patients, reinforcing RA Receptor (RAR) signalling as a promising therapeutic strategy. In this review we provide a holistic approach focussing on the effects of isoform-specific RAR modulation with respect to APP secretases and discuss its advantages and drawbacks in subcellular AD related events.

PRMT5-mediated RNF4 methylation promotes therapeutic resistance of APL cells to As2O3 by stabilizing oncoprotein PML-RARα.

Acute promyelocytic leukemia (APL) is a hematological malignancy driven by the oncoprotein PML-RARα, which can be treated with arsenic trioxide (As2O3) or/and all-trans retinoic acid. The protein arginine methyltransferase 5 (PRMT5) is involved in tumorigenesis. However, little is known about the biological function and therapeutic potential of PRMT5 in APL. Here, we show that PRMT5 is highly expressed in APL patients. PRMT5 promotes APL by interacting with PML-RARα and suppressing its ubiquitination and degradation. Mechanistically, PRMT5 attenuates the interaction between PML-RARα and its ubiquitin E3 ligase RNF4 by methylating RNF4 at Arg164. Notably, As2O3 treatment triggers the dissociation of PRMT5 from PML nuclear bodies, attenuating RNF4 methylation and promoting RNF4-mediated PML-RARα ubiquitination and degradation. Moreover, knockdown of PRMT5 and pharmacological inhibition of PRMT5 with the specific inhibitor EPZ015666 significantly inhibit APL cells growth. The combination of EPZ015666 with As2O3 shows synergistic effects on As2O3-induced differentiation of bone marrow cells from APL mice, as well as on apoptosis and differentiation of primary APL cells from APL patients. These findings provide mechanistic insight into the function of PRMT5 in APL pathogenesis and demonstrate that inhibition of PRMT5, alone or in combination with As2O3, might be a promising therapeutic strategy against APL.

Insertion/deletion (Indel) variant of the goat RORA gene is associated with growth traits.

RAR related orphan receptor A (RORA), which encodes the retinoid-acid-related orphan receptor alpha (RORα), is a clock gene found in skeletal muscle. Several studies have shown that RORα plays an important role in bone formation, suggesting that RORA gene may take part in the regulation of growth and development. The purpose of this research is to study the insertion/deletion (indel) variations of the RORA gene and investigate the relationship with the growth traits of Shaanbei white cashmere (SBWC) goats. Herein, the current study identified that the P4-11-bp and P11-28-bp deletion sites are polymorphic among 12 pairs of primers within the RORA gene in the SBWC goats (n = 641). Moreover, the P11-28-bp deletion locus was significantly related to the body height (p = 0.046), height at hip cross (p = 0.012), and body length (p = 0.003). Both of P4-11-bp and P11-28-bp indels showed the moderate genetic diversity (0.25