The elemental mechanism of transcriptional pausing.

Transcriptional pausing underlies regulation of cellular RNA biogenesis. A consensus pause sequence that acts on RNA polymerases (RNAPs) from bacteria to mammals halts RNAP in an elemental paused state from which longer-lived pauses can arise. Although the structural foundations of pauses prolonged by backtracking or nascent RNA hairpins are recognized, the fundamental mechanism of the elemental pause is less well-defined. Here we report a mechanistic dissection that establishes the elemental pause signal (i) is multipartite; (ii) causes a modest conformational shift that puts γ-proteobacterial RNAP in an off-pathway state in which template base loading but not RNA translocation is inhibited; and (iii) allows RNAP to enter pretranslocated and one-base-pair backtracked states easily even though the half-translocated state observed in paused cryo-EM structures rate-limits pause escape. Our findings provide a mechanistic basis for the elemental pause and a framework to understand how pausing is modulated by sequence, cellular conditions, and regulators

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Phytochemicals as Invaluable Sources of Potent Antimicrobial Agents to Combat Antibiotic Resistance

Plants have been used for therapeutic purposes against various human ailments for several centuries. Plant-derived natural compounds have been implemented in clinics against microbial diseases. Unfortunately, the emergence of antimicrobial resistance has significantly reduced the efficacy of existing standard antimicrobials. The World Health Organization (WHO) has declared antimicrobial resistance as one of the top 10 global public health threats facing humanity. Therefore, it is the need of the hour to discover new antimicrobial agents against drug-resistant pathogens. In the present article, we have discussed the importance of plant metabolites in the context of their medicinal applications and elaborated on their mechanism of antimicrobial action against human pathogens. The WHO has categorized some drug-resistant bacteria and fungi as critical and high priority based on the need to develope new drugs, and we have considered the plant metabolites that target these bacteria and fungi. We have also emphasized the role of phytochemicals that target deadly viruses such as COVID-19, Ebola, and dengue. Additionally, we have also elaborated on the synergetic effect of plant-derived compounds with standard antimicrobials against clinically important microbes. Overall, this article provides an overview of the importance of considering phytogenous compounds in the development of antimicrobial compounds as therapeutic agents against drug-resistant microbes

Idiopathic intracranial hypertension following levothyroxine replacement therapy: Systematic review and a case report

The data on the characteristics of patients with idiopathic intracranial hypertension (IIH) following levothyroxine (LT4) replacement are limited. Here, we report a case and systematically review published cases of idiopathic intracranial hypertension (IIH) following levothyroxine (LT4) replacement. The systematic review was performed as per the PRISMA guidelines. Our patient is a 46-year-old lady with hypothyroidism (thyrotropin: 319 mIU/L, free thyroxine: 0.04 ng/dl), treated with 100 μg.d of LT4 and presented a month later with headache, visual diminution, bilateral lateral rectus palsies, and papilledema. Cerebrospinal fluid (CSF) pressure was 32 cmH2O. Drainage of CSF, oral acetazolamide, and modification of LT4 dose resulted in prompt symptomatic improvement and complete reversal of IIH. In the systematic review (n = 21), the median age of patients (7 males) was 13 (IQR: 8.8- 26.5) years. The median duration of hypothyroid symptoms was 4 (n = 10, IQR: 0.44-6.25) years whereas that from initiation of LT4 replacement to the diagnosis of IIH was 2 (n = 20, IQR: 1.17-4) months. Initial median serum thyrotropin and thyroxine were 100 (n = 14, IQR: 72.5-421.6) mIU/L, and 1.13 (n = 12, IQR: 1.0-2.45) μg/dl which changed to 2.2 (n = 7; IQR: 0.23-3.40) mIU/L and 8.90 μg/dl (n = 8, IQR: 6.43-14.85 μg/dl), respectively at diagnosis of IIH after LT4 treatment with median daily LT4 doses of 0.89 (n = 8, IQR: 0.60 – 1.17) times the maximum recommended dose for age. To conclude, we report an adult woman with IIH following LT4 replacement for primary hypothyroidism, a rare entity. Pediatric age, prolonged symptom duration, and use of higher LT4 replacement dose may be associated with IIH following LT4 replacement

Small molecule based five-membered heterocycles: A view of liquid crystalline properties beyond the biological applications

Liquid crystal (LC) is an intermediate phase of matter with the physical attributes of liquid, and a high-level of orientational order of solids. This property of LCs has been widely utilized for the development of LC displays and other industrial applications. The research in the past few decades shows the substantial increase in the exploring of applications of five-membered liquid crystalline heterocydes in photovoltaic devices, organic light-emitting technologies, and biological systems. In this article, we have discussed the history, classification, synthetic strategies, physical parameters and mesomorphic studies of five-membered heterocycles beyond biological applications. The liquid crystalline heterocycles that are covered in the review include imidazoles, isoxazoles, isoxazolines, pyrazoles, pyrazolines, thiazoles, thiophenes, 1,2,3- and 1,2,4-triazoles, 1,2,4- and 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles. Overall, the review provides a comprehensive profile of the mesomorphic properties of five-membered heterocydes. (C) 2019 Elsevier B.V. All rights reserved

A pause sequence enriched at translation start sites drives transcription dynamics in vivo

Transcription by RNA polymerase (RNAP) is interrupted by pauses that play diverse regulatory roles. Although individual pauses have been studied in vitro, the determinants of pauses in vivo and their distribution throughout the bacterial genome remain unknown. Using nascent transcript sequencing, we identified a 16-nucleotide consensus pause sequence in Escherichia coli that accounts for known regulatory pause sites as well as ~20,000 new in vivo pause sites. In vitro single-molecule and ensemble analyses demonstrate that these pauses result from RNAP-nucleic acid interactions that inhibit next-nucleotide addition. The consensus sequence also leads to pausing by RNAPs from diverse lineages and is enriched at translation start sites in both E. coli and Bacillus subtilis. Our results thus reveal a conserved mechanism unifying known and newly identified pause events

A Promoter Recognition Mechanism Common to Yeast Mitochondrial and Phage T7 RNA Polymerases*S⃞

Yeast mitochondrial (YMt) and phage T7 RNA polymerases (RNAPs) are two divergent representatives of a large family of single subunit RNAPs that are also found in the mitochondria and chloroplasts of higher eukaryotes, mammalian nuclei, and many other bacteriophage. YMt and phage T7 promoters differ greatly in sequence and length, and the YMt RNAP uses an accessory factor for initiation, whereas T7 RNAP does not. We obtain evidence here that, despite these apparent differences, both the YMt and T7 RNAPs utilize a similar promoter recognition loop to bind their respective promoters. Mutations in this element in YMt RNAP specifically disrupt mitochondrial promoter utilization, and experiments with site-specifically tethered chemical nucleases indicate that this element binds the mitochondrial promoter almost identically to how the promoter recognition loop from the phage RNAP binds its promoter. Sequence comparisons reveal that the other members of the single subunit RNAP family display loops of variable sequence and size at a position corresponding to the YMt and T7 RNAP promoter recognition loops. We speculate that these elements may be involved in promoter recognition in most or all of these enzymes and that this element's structure allows it to accommodate significant sequence and length variation to provide a mechanism for rapid evolution of new promoter specificities in this RNAP family