Rn7SK small nuclear RNA is involved in neuronal differentiation

7SK small nuclear RNA (Rn7SK) induces apoptosis through intrinsic and extrinsic pathways in human embryonic kidney cell line

BACKGROUND

Rn7SK, a highly conserved small nuclear non-coding RNA, controls Polymerase II transcription machinery by activating of the Positive Transcriptional Elongation Factor b (P-TEFb). Apart from its role in transcriptional regulation, the potential functions of Rn7SK in cell apoptosis are poorly understood. In a previous study, we demonstrated that overexpression of 7SK induces apoptosis in HEK cells. However, it remains unclear whether 7SK-mediated apoptosis induction is exerted through the intrinsic or extrinsic pathways.

METHODS AND RESULTS

Rn7SK was overexpressed in HEK 293T cell line using Lipofectamine 2000 reagent to investigate its potential apoptotic functions. The overexpression of Rn7SK resulted in reduced cell viability through the induction of apoptosis, as evidenced by MTT assay and Annexin V/PI staining. Concurrently, alterations in the expression levels of key apoptosis-related genes were observed, as determined by quantitative RT-PCR. Furthermore, Rn7SK overexpression led to a decrease in cell proliferation, as assessed by colony formation assay and growth curve analysis. This reduction was associated with downregulated expression of key proliferative-related genes. Additionally, the migration and invasion capabilities of cells were significantly inhibited upon upregulation of Rn7SK, as demonstrated by transwell assays.

CONCLUSIONS

This study suggests the apoptotic role of 7SK through both intrinsic and extrinsic pathways, necessitating further investigation into its underlying mechanisms.

Efficient Neural Differentiation of Mouse Embryonic Stem Cells by Mastic Gum

Purpose: Promoting neurogenesis is a promising strategy to treat neurodegenerative disorders. In the present study, we aimed to evaluate the effect of mastic gum resin from the Pistacia lentiscus var. Chia (Anacardiaceae family) in proliferation capacity and differentiation of embryonic mesenchymal stem cells into a neural lineage. Methods: For this purpose, mastic gum was applied as a neural inducer for stem cell differentiation into the neuronal lineage. Following treatment of embryonic stem cells (ESCs) with mastic gum, verification differentiation of the ESCs into the neuronal lineage, gene expression analysis, and immunocytochemistry staining approach were performed. Results: Gene expression analysis demonstrated that mastic gum increased the expression level of neuron markers in the ESCs-derived neuron-like cells. Moreover, our immunocytochemistry staining results of two important neural stem cell markers, including Nestin and microtubule-associated protein-2 (Map2) expression confirmed that mastic gum has the potential to promote neuronal differentiation in ESCs. Conclusion: In summary, the use of mastic gum to stimulate the differentiation of ESCs into a neural lineage can be considered as a good candidate in stem cell therapy.

LPI-HyADBS: a hybrid framework for lncRNA-protein interaction prediction integrating feature selection and classification

Background

Long noncoding RNAs (lncRNAs) have dense linkages with a plethora of important cellular activities. lncRNAs exert functions by linking with corresponding RNA-binding proteins. Since experimental techniques to detect lncRNA-protein interactions (LPIs) are laborious and time-consuming, a few computational methods have been reported for LPI prediction. However, computation-based LPI identification methods have the following limitations: (1) Most methods were evaluated on a single dataset, and researchers may thus fail to measure their generalization ability. (2) The majority of methods were validated under cross validation on lncRNA-protein pairs, did not investigate the performance under other cross validations, especially for cross validation on independent lncRNAs and independent proteins. (3) lncRNAs and proteins have abundant biological information, how to select informative features need to further investigate.

Results

Under a hybrid framework (LPI-HyADBS) integrating feature selection based on AdaBoost, and classification models including deep neural network (DNN), extreme gradient Boost (XGBoost), and SVM with a penalty Coefficient of misclassification (C-SVM), this work focuses on finding new LPIs. First, five datasets are arranged. Each dataset contains lncRNA sequences, protein sequences, and an LPI network. Second, biological features of lncRNAs and proteins are acquired based on Pyfeat. Third, the obtained features of lncRNAs and proteins are selected based on AdaBoost and concatenated to depict each LPI sample. Fourth, DNN, XGBoost, and C-SVM are used to classify lncRNA-protein pairs based on the concatenated features. Finally, a hybrid framework is developed to integrate the classification results from the above three classifiers. LPI-HyADBS is compared to six classical LPI prediction approaches (LPI-SKF, LPI-NRLMF, Capsule-LPI, LPI-CNNCP, LPLNP, and LPBNI) on five datasets under 5-fold cross validations on lncRNAs, proteins, lncRNA-protein pairs, and independent lncRNAs and independent proteins. The results show LPI-HyADBS has the best LPI prediction performance under four different cross validations. In particular, LPI-HyADBS obtains better classification ability than other six approaches under the constructed independent dataset. Case analyses suggest that there is relevance between ZNF667-AS1 and Q15717.

Conclusions

Integrating feature selection approach based on AdaBoost, three classification techniques including DNN, XGBoost, and C-SVM, this work develops a hybrid framework to identify new linkages between lncRNAs and proteins.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04485-x.

RN7SK small nuclear RNA controls bidirectional transcription of highly expressed gene pairs in skin

Pausing of RNA polymerase II (Pol II) close to promoters is a common regulatory step in RNA synthesis, and is coordinated by a ribonucleoprotein complex scaffolded by the noncoding RNA RN7SK. The function of RN7SK-regulated gene transcription in adult tissue homoeostasis is currently unknown. Here, we deplete RN7SK during mouse and human epidermal stem cell differentiation. Unexpectedly, loss of this small nuclear RNA specifically reduces transcription of numerous cell cycle regulators leading to cell cycle exit and differentiation. Mechanistically, we show that RN7SK is required for efficient transcription of highly expressed gene pairs with bidirectional promoters, which in the epidermis co-regulated cell cycle and chromosome organization. The reduction in transcription involves impaired splicing and RNA decay, but occurs in the absence of chromatin remodelling at promoters and putative enhancers. Thus, RN7SK is directly required for efficient Pol II transcription of highly transcribed bidirectional gene pairs, and thereby exerts tissue-specific functions, such as maintaining a cycling cell population in the epidermis.

The noncoding RNA RN7SK regulates RNA polymerase II pausing and splicing. Here the authors deplete RN7SK in mouse and human during epidermal stem cell differentiation and reveal a novel role in orchestrating bidirectional transcription of highly expressed gene pairs.

[7SK truncation at 128-179 nt suppresses embryonic stem cell proliferation in vitro by downregulating CDC6]

OBJECTIVE

To explore the role of small nuclear noncoding RNA 7SK in embryonic stem cell (ESCs) proliferation and the value of 7SK as a target for early diagnosis and treatment for primordial dwarfism (PD).

METHODS

ESC line R1 was transfected with the CRISPR/Cas9 system, and sequencing of the PCR product and glycerol gradient analysis were performed to identify novel 7SK deletion mutations. A lentivirus system was used to knock down cyclin-dependent kinase 9 (CDK9) in clones with 7SK deletion mutations, and the effect of CDK9 knockdown on the protein level of cell division cycle 6 (CDC6) was analyzed with Western blotting.

RESULTS

We identified a novel deletion mutation of 7SK at 128-179 nt in the ESCs, which resulted in deficiency of cell proliferation. 7SK truncation at 128-179 nt significantly reduced the protein expressions of La-related protein 7 (LARP7) and CDC6.

CONCLUSIONS

7SK truncation at 128-179 nt can significantly impair proliferation of ESCs by downregulating CDC6. 7SK is a key regulator of proliferation and mediates the growth of ESCs through a mechanism dependent on CDK9 activity, suggesting the value of 7SK truncation at 128-179 nt as a potential target for early diagnosis and treatment of PD.

Keeping the balance: The noncoding RNA 7SK as a master regulator for neuron development and function

The noncoding RNA 7SK is a critical regulator of transcription by adjusting the activity of the kinase complex P-TEFb. Release of P-TEFb from 7SK stimulates transcription at many genes by promoting productive elongation. Conversely, P-TEFb sequestration by 7SK inhibits transcription. Recent studies have shown that 7SK functions are particularly important for neuron development and maintenance and it can thus be hypothesized that 7SK is at the center of many signaling pathways contributing to neuron function. 7SK activates neuronal gene expression programs that are key for terminal differentiation of neurons. Proteomics studies revealed a complex protein interactome of 7SK that includes several RNA-binding proteins. Some of these novel 7SK subcomplexes exert non-canonical cytosolic functions in neurons by regulating axonal mRNA transport and fine-tuning spliceosome production in response to transcription alterations. Thus, a picture emerges according to which 7SK acts as a multi-functional RNA scaffold that is integral for neuron homeostasis.

Deconstructing Stepwise Fate Conversion of Human Fibroblasts to Neurons by MicroRNAs

Cell-fate conversion generally requires reprogramming effectors to both introduce fate programs of the target cell type and erase the identity of starting cell population. Here, we reveal insights into the activity of microRNAs miR-9/9∗ and miR-124 (miR-9/9∗-124) as reprogramming agents that orchestrate direct conversion of human fibroblasts into motor neurons by first eradicating fibroblast identity and promoting uniform transition to a neuronal state in sequence. We identify KLF-family transcription factors as direct target genes for miR-9/9∗-124 and show their repression is critical for erasing fibroblast fate. Subsequent gain of neuronal identity requires upregulation of a small nuclear RNA, RN7SK, which induces accessibilities of chromatin regions and neuronal gene activation to push cells to a neuronal state. Our study defines deterministic components in the microRNA-mediated reprogramming cascade.

Noncoding RNAs Set the Stage for RNA Polymerase II Transcription

Effective synthesis of mammalian messenger (m)RNAs depends on many factors that together direct RNA polymerase II (pol II) through the different stages of the transcription cycle and ensure efficient cotranscriptional processing of mRNAs. In addition to the many proteins involved in transcription initiation, elongation, and termination, several noncoding (nc)RNAs also function as global transcriptional regulators. Understanding the mode of action of these non-protein regulators has been an intense area of research in recent years. Here, we describe how these ncRNAs influence key regulatory steps of the transcription process, to affect large numbers of genes. Through direct association with pol II or by modulating the activity of transcription or RNA processing factors, these regulatory RNAs perform critical roles in gene expression.

de novo MEPCE nonsense variant associated with a neurodevelopmental disorder causes disintegration of 7SK snRNP and enhanced RNA polymerase II activation

In eukaryotes, the elongation phase of transcription by RNA polymerase II (RNAP II) is regulated by the transcription elongation factor b (P-TEFb), composed of Cyclin-T1 and cyclin-dependent kinase 9. The release of RNAP II is mediated by phosphorylation through P-TEFb that in turn is under control by the inhibitory 7SK small nuclear ribonucleoprotein (snRNP) complex. The 7SK snRNP consists of the 7SK non-coding RNA and the proteins MEPCE, LARP7, and HEXIM1/2. Biallelic LARP7 loss-of-function variants underlie Alazami syndrome characterized by growth retardation and intellectual disability. We report a boy with global developmental delay and seizures carrying the de novo MEPCE nonsense variant c.1552 C > T/p.(Arg518*). mRNA and protein analyses identified nonsense-mediated mRNA decay to underlie the decreased amount of MEPCE in patient fibroblasts followed by LARP7 and 7SK snRNA downregulation and HEXIM1 upregulation. Reduced binding of HEXIM1 to Cyclin-T1, hyperphosphorylation of the RNAP II C-terminal domain, and upregulated expression of ID2, ID3, MRPL11 and snRNAs U1, U2 and U4 in patient cells are suggestive of enhanced activation of P-TEFb. Flavopiridol treatment and ectopic MEPCE protein expression in patient fibroblasts rescued increased expression of six RNAP II-sensitive genes and suggested a possible repressive effect of MEPCE on P-TEFb-dependent transcription of specific genes.

Rn7SK small nuclear RNA is involved in cellular senescence

Rn7SK is a conserved small nuclear noncoding RNA which its function in aging has not been studied. Recently, we have demonstrated that Rn7SK overexpression reduces cell viability and is significantly downregulated in stem cells, human tumor tissues, and cell lines. In this study, we analyzed the role of Rn7SK on senescence in adipose tissue-derived mesenchymal stem cells (AD-MSCs). For this purpose, Rn7SK expression was downregulated and upregulated via transfection and transduction, respectively, in AD-MSCs and subsequently, various distinct characteristics of senescence including cell viability, proliferation, colony formation, senescence-associated β galactosidase activity, and differentiation potency was analyzed. Our results demonstrated the transient knockdown of Rn7SK in MSCs leads to delayed senescence, while its overexpressions shows opposite effects. When osteogenic differentiation was started, however, they exhibited a greater differentiation potential than the original MSCs, suggesting a potential tool for stem cell-based regenerative medicine.

OKN-007 Increases temozolomide (TMZ) Sensitivity and Suppresses TMZ-Resistant Glioblastoma (GBM) Tumor Growth

Treatment of glioblastoma (GBM) remains a challenge using conventional chemotherapy, such as temozolomide (TMZ), and is often ineffective as a result of drug resistance. We have assessed a novel nitrone-based agent, OKN-007, and found it to be effective in decreasing tumor volumes and increasing survival in orthotopic GBM xenografts by decreasing cell proliferation and angiogenesis and increasing apoptosis. In this study, we assessed combining OKN-007 with TMZ in vivo in a human G55 GBM orthotopic xenograft model and in vitro in TMZ-resistant and TMZ-sensitive human GBM cell lines. For the in vivo studies, magnetic resonance imaging was used to assess tumor growth and vascular alterations. Percent animal survival was also determined. For the in vitro studies, cell growth, IC50 values, RNA-seq, RT-PCR, and ELISA were used to assess growth inhibition, possible mechanism-of actions (MOAs) associated with combined OKN-007 + TMZ versus TMZ alone, and gene and protein expression levels, respectively. Microarray analysis of OKN-007-treated rat F98 glioma tumors was also carried out to determine possible MOAs of OKN-007 in glioma-bearing animals either treated or not treated with OKN-007. OKN-007 seems to elicit its effect on GBM tumors via inhibition of tumorigenic TGF-β1, which affects the extracellular matrix. When combined with TMZ, OKN-007 significantly increases percent survival, decreases tumor volumes, and normalizes tumor blood vasculature in vivo compared to untreated tumors and seems to affect TMZ-resistant GBM cells possibly via IDO-1, SUMO2, and PFN1 in vitro. Combined OKN-007 + TMZ may be a potentially potent treatment strategy for GBM patients.