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Aim of the present study was to investigate the influence of the angiotensin II (ANG II) subtype 1 (AT1) receptor blockers fonsartan and losartan on blood pressure, cardiac -dynamics and -metabolism as well as functional and morphological changes in the kidney of rats after long-term inhibition of the nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME). Oral chronic treatment with L-NAME in a dose of 25 mg/kg/d over 6 weeks caused a significant increase in systolic blood pressure (198±13 mmHg) when compared to untreated rats (144±4 mmHg). Animals receiving simultaneously L-NAME and fonsartan (10 mg/kg/d) or losartan (30 mg/kg/d) were protected against blood pressure increase. L-NAME treatment caused a significant decrease in glomerular filtration rate (GFR) from 4.52±0.81 to 1.34±0.26 ml/kg-1/min-1 and renal plasma flow (RPF) from 10.52±1.29 ml/kg-1/min-1 to 5.66±1.06 ml/kg-1/min-1. Co-treatment with fonsartan and losartan prevented L-NAME-induced reduction in GFR and RPF. There was no difference in urine, sodium and potassium excretion in groups under investigation. Plasma renin activity (PRA) was further stimulated by fonsartan and losartan treatment. L-NAME produced a significant elevation in urinary protein excretion which was antagonised by both AT1 blockers. Isolated hearts from animals treated with L-NAME showed a significant prolongation in the duration of ventricular fibrillation and a significant decrease in coronary flow as compared to control hearts. Treatment with fonsartan and losartan significantly decreased the duration of ventricular fibrillation as compared to L-NAME group. In addition, both AT1 blockers given alone significantly reduced the duration of ventricular fibrillation as compared to hearts from untreated controls. During ischemia the cytosolic enzymes lactate dehydrogenase and creatine kinase as well as lactate in the coronary effluent were significantly increased in the L-NAME group. Myocardial tissue values of glycogen, ATP, and creatine phosphate were decreased, whereas lactate was increased. Fonsartan and losartan treatment totally abolished these effects. Histological examination of kidneys revealed that simultaneous administration of fonsartan and losartan with L-NAME abolished L-NAME-induced arteriolar hyalinosis, segmental sclerosis of glomerular capillaries and focal tubular atrophies. In conclusion, long-term blockade of ANG II subtype AT1 receptors by fonsartan and losartan prevented L-NAME-induced hypertension, renal insufficiency, as well as cardio-dynamic, cardio-metabolic, and morphological deteriorations. [ABSTRACT FROM AUTHOR]

Steroid hormone receptors are ligand-binding transcription factors essential for mammalian physiology. The androgen receptor (AR) binds androgens mediating gene expression for sexual, somatic and behavioural functions, and is involved in various conditions including androgen insensitivity syndrome and prostate cancer 1 . Here we identified functional mutations in the formin and actin nucleator DAAM2 in patients with androgen insensitivity syndrome. DAAM2 was enriched in the nucleus, where its localization correlated with that of the AR to form actin-dependent transcriptional droplets in response to dihydrotestosterone. DAAM2 AR droplets ranged from 0.02 to 0.06 µm 3 in size and associated with active RNA polymerase II. DAAM2 polymerized actin directly at the AR to promote droplet coalescence in a highly dynamic manner, and nuclear actin polymerization is required for prostate-specific antigen expression in cancer cells. Our data uncover signal-regulated nuclear actin assembly at a steroid hormone receptor necessary for transcription., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

RNA polymerase (Pol) III is specialized to transcribe short, abundant RNAs, for which it terminates transcription on polythymine (dT) stretches on the non-template (NT) strand. When Pol III reaches the termination signal, it pauses and forms the pre-termination complex (PTC). Here, we report cryoelectron microscopy (cryo-EM) structures of the yeast Pol III PTC and complementary functional states at resolutions of 2.7-3.9 Å. Pol III recognizes the poly(dT) termination signal with subunit C128 that forms a hydrogen-bond network with the NT strand and, thereby, induces pausing. Mutating key interacting residues interferes with transcription termination in vitro, impairs yeast growth, and causes global termination defects in vivo, confirming our structural results. Additional cryo-EM analysis reveals that C53-C37, a Pol III subcomplex and key termination factor, participates indirectly in Pol III termination. We propose a mechanistic model of Pol III transcription termination and rationalize why Pol III, unlike Pol I and Pol II, terminates on poly(dT) signals., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

RNA polymerase I (Pol I) specifically synthesizes ribosomal RNA. Pol I upregulation is linked to cancer, while mutations in the Pol I machinery lead to developmental disorders. Here we report the cryo-EM structure of elongating human Pol I at 2.7 Å resolution. In the exit tunnel, we observe a double-stranded RNA helix that may support Pol I processivity. Our structure confirms that human Pol I consists of 13 subunits with only one subunit forming the Pol I stalk. Additionally, the structure of human Pol I in complex with the initiation factor RRN3 at 3.1 Å resolution reveals stalk flipping upon RRN3 binding. We also observe an inactivated state of human Pol I bound to an open DNA scaffold at 3.3 Å resolution. Lastly, the high-resolution structure of human Pol I allows mapping of disease-related mutations that can aid understanding of disease etiology., (© 2021. The Author(s).)

RNA polymerase III (Pol III) synthesizes transfer RNAs and other short, essential RNAs. Human Pol III misregulation is linked to tumor transformation, neurodegenerative and developmental disorders, and increased sensitivity to viral infections. Here, we present cryo-electron microscopy structures at 2.8 to 3.3 Å resolution of transcribing and unbound human Pol III. We observe insertion of the TFIIS-like subunit RPC10 into the polymerase funnel, providing insights into how RPC10 triggers transcription termination. Our structures resolve elements absent from Saccharomyces cerevisiae Pol III such as the winged-helix domains of RPC5 and an iron-sulfur cluster, which tethers the heterotrimer subcomplex to the core. The cancer-associated RPC7α isoform binds the polymerase clamp, potentially interfering with Pol III inhibition by tumor suppressor MAF1, which may explain why overexpressed RPC7α enhances tumor transformation. Finally, the human Pol III structure allows mapping of disease-related mutations and may contribute to the development of inhibitors that selectively target Pol III for therapeutic interventions.

Transcription factor (TF) IIIC is a conserved eukaryotic six-subunit protein complex with dual function. It serves as a general TF for most RNA polymerase (Pol) III genes by recruiting TFIIIB, but it is also involved in chromatin organization and regulation of Pol II genes through interaction with CTCF and condensin II. Here, we report the structure of the S. cerevisiae TFIIIC subcomplex τA, which contains the most conserved subunits of TFIIIC and is responsible for recruitment of TFIIIB and transcription start site (TSS) selection at Pol III genes. We show that τA binding to its promoter is auto-inhibited by a disordered acidic tail of subunit τ95. We further provide a negative-stain reconstruction of τA bound to the TFIIIB subunits Brf1 and TBP. This shows that a ruler element in τA achieves positioning of TFIIIB upstream of the TSS, and suggests remodeling of the complex during assembly of TFIIIB by TFIIIC.

Ubiquitin C-terminal hydrolase deubiquitinase BAP1 is an essential tumor suppressor involved in cell growth control, DNA damage response, and transcriptional regulation. As part of the Polycomb repression machinery, BAP1 is activated by the deubiquitinase adaptor domain of ASXL1 mediating gene repression by cleaving ubiquitin (Ub) from histone H2A in nucleosomes. The molecular mechanism of BAP1 activation by ASXL1 remains elusive, as no structures are available for either BAP1 or ASXL1. Here, we present the crystal structure of the BAP1 ortholog from Drosophila melanogaster, named Calypso, bound to its activator, ASX, homolog of ASXL1. Based on comparative structural and functional analysis, we propose a model for Ub binding by Calypso/ASX, uncover decisive structural elements responsible for ASX-mediated Calypso activation, and characterize the interaction with ubiquitinated nucleosomes. Our results give molecular insight into Calypso function and its regulation by ASX and provide the opportunity for the rational design of mechanism-based therapeutics to treat human BAP1/ASXL1-related tumors., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Oxysterol binding protein-related proteins (ORPs) are conserved lipid binding polypeptides, enriched at ER contacts sites. ORPs promote non-vesicular lipid transport and work as lipid sensors in the context of many cellular tasks, but the determinants of their distinct localization and function are not understood. Here, we demonstrate that the yeast endocytic invaginations associate with the ER and that this association specifically requires the ORPs Osh2 and Osh3, which bridge the endocytic myosin-I Myo5 to the ER integral-membrane VAMP-associated protein (VAP) Scs2. Disruption of the ER contact with endocytic sites using ORP, VAP, myosin-I, or reticulon mutants delays and weakens actin polymerization and interferes with vesicle scission. Finally, we provide evidence suggesting that ORP-dependent sterol transfer facilitates actin polymerization at endocytic sites., (Copyright © 2017 Elsevier Inc. All rights reserved.)