Pharmacologic targeting of the P-TEFb complex as a therapeutic strategy for chronic myeloid leukemia.

BACKGROUND: The positive transcription elongation factor b (P-TEFb) kinase activity is involved in the process of transcription. Cyclin-dependent kinase 9 (CDK9), a core component of P-TEFb, regulates the process of transcription elongation, which is associated with differentiation and apoptosis in many cancer types. Wogonin, a natural CDK9 inhibitor isolated from Scutellaria baicalensis. This study aimed to investigate the involved molecular mechanisms of wogonin on anti- chronic myeloid leukemia (CML) cells. MATERIALS AND METHODS: mRNA and protein levels were analysed by RT-qPCR and western blot. Flow cytometry was used to assess cell differentiation and apoptosis. Cell transfection, immunofluorescence analysis and co-immunoprecipitation (co-IP) assays were applied to address the potential regulatory mechanism of wogonin. KU-812 cells xenograft NOD/SCID mice model was used to assess and verify the mechanism in vivo. RESULTS: We reported that the anti-CML effects in K562, KU-812 and primary CML cells induced by wogonin were regulated by P-TEFb complex. We also confirmed the relationship between CDK9 and erythroid differentiation via knockdown the expression of CDK9. For further study the mechanism of erythroid differentiation induced by wogonin, co-IP experiments were used to demonstrate that wogonin increased the binding between GATA-1 and FOG-1 but decreased the binding between GATA-1 and RUNX1, which were depended on P-TEFb. Also, wogonin induced apoptosis and decreased the mRNA and protein levels of MCL-1 in KU-812 cells, which is the downstream of P-TEFb. In vivo studies showed wogonin had good anti-tumor effects in KU-812 xenografts NOD/ SCID mice model and decreased the proportion of human CD45+ cells in spleens of mice. We also verified that wogonin exhibited anti-CML effects through modulating P-TEFb activity in vivo. CONCLUSIONS: Our study indicated a special mechanism involving the regulation of P-TEFb kinase activity in CML cells, providing evidences for further application of wogonin in CML clinical treatment. Video Abstract.

Lithocholic Acid Improves the Survival of Drosophila Melanogaster.

SCOPE: Primary bile acids are produced in the liver, whereas secondary bile acids, such as lithocholic acid (LCA), are generated by gut bacteria from primary bile acids that escape the ileal absorption. Besides their well-known function as detergents in lipid digestion, bile acids are important signaling molecules mediating effects on the host's metabolism. METHODS AND RESULTS: Fruit flies (Drosophila melanogaster) are supplemented with 50 µmol L-1 LCA either for 30 days or throughout their lifetime. LCA supplementation results in a significant induction of the mean (+12 days), median (+10 days), and maximum lifespan (+ 11 days) in comparison to untreated control flies. This lifespan extension is accompanied by an induction of spargel (srl), the fly homolog of mammalian PPAR-γ co-activator 1α (PGC1α). In wild-type flies, the administration of antibiotics abrogates both the LCA-mediated lifespan induction as well as the upregulation of srl. CONCLUSION: It is shown that the secondary bile acid LCA significantly induces the mean, the median, and the maximum survival in D. melanogaster. Our data suggest that besides an upregulation of the PGC1α-homolog srl, unidentified alterations in the structure or metabolism of the gut microbiota contribute to the longevity effect mediated by LCA.

Protective effect of berberine on antioxidant enzymes and positive transcription elongation factor b expression in diabetic rat liver.

The protective effect of berberine against antioxidant, antilipid peroxidation in serum and liver tissue, and positive transcription elongation factor b (P-TEFb) expression in liver tissue of type 2 diabetic rats was investigated. Overnight fasted rats were intraperitoneally injected 35 mg/kg streptozotocin. Diabetic rats were admitted after 2 weeks and given a high-carbohydrate/high-fat diet to induce hyperlipidemias. From week 16, diabetic rats were treated with 75, 150, 300 mg/kg berberine, 100mg/kg fenofibrate or 4 mg/kg rosiglitazone for another 16 weeks. P-TEFb (composed of cyclin-dependent kinase 9 and cyclin T1) mRNA and protein expression in liver tissue were detected by real time PCR and immunohistochemistry, respectively. Berberine significantly up-regulated the declined cyclin-dependent kinase 9, cyclin T1 mRNA and protein expression in diabetic rat liver. Berberine obviously decreased malondialdehyde level and increased catalase, superoxide dismutase, glutathione peroxidase, and glutathione activities in liver tissue and serum of diabetic rats. These results suggest that the effects of berberine on up-regulation of P-TEFb expression, antioxidant and antilipid peroxidation may be related to its protective potential on diabetes.

The Yin and Yang of P-TEFb regulation: implications for human immunodeficiency virus gene expression and global control of cell growth and differentiation.

The positive transcription elongation factor b (P-TEFb) stimulates transcriptional elongation by phosphorylating the carboxy-terminal domain of RNA polymerase II and antagonizing the effects of negative elongation factors. Not only is P-TEFb essential for transcription of the vast majority of cellular genes, but it is also a critical host cellular cofactor for the expression of the human immunodeficiency virus (HIV) type 1 genome. Given its important role in globally affecting transcription, P-TEFb's activity is dynamically controlled by both positive and negative regulators in order to achieve a functional equilibrium in sync with the overall transcriptional demand as well as the proliferative state of cells. Notably, this equilibrium can be shifted toward either the active or inactive state in response to diverse physiological stimuli that can ultimately affect the cellular decision between growth and differentiation. In this review, we examine the mechanisms by which the recently identified positive (the bromodomain protein Brd4) and negative (the noncoding 7SK small nuclear RNA and the HEXIM1 protein) regulators of P-TEFb affect the P-TEFb-dependent transcriptional elongation. We also discuss the consequences of perturbations of the dynamic associations of these regulators with P-TEFb in relation to the pathogenesis and progression of several major human diseases, such as cardiac hypertrophy, breast cancer, and HIV infection.