Escherichia coli NusG links the lead ribosome with the transcription elongation complex

It has been known for more than 50 years that transcription and translation are physically coupled in bacteria, but whether or not this coupling may be mediated by the two-domain protein N-utilization substance (Nus) G in Escherichia coli is still heavily debated. Here, we combine integrative structural biology and functional analyses to provide conclusive evidence that NusG can physically link transcription with translation by contacting both RNA polymerase and the ribosome. We present a cryo-electron microscopy structure of a NusG:70S ribosome complex and nuclear magnetic resonance spectroscopy data revealing simultaneous binding of NusG to RNAP and the intact 70S ribosome, providing the first direct structural evidence for NusG-mediated coupling. Furthermore, in vivo reporter assays show that recruitment of NusG occurs late in transcription and strongly depends on translation. Thus, our data suggest that coupling occurs initially via direct RNAP:ribosome contacts and is then mediated by NusG.

Histone Deacetylase Inhibitors and Antioxidants From the Root of Gluta usitata

A new glycoside, glutacoside (1), as well as 6 known compounds was isolated and identified from the root of Gluta usitata. Their structures were determined by Infrared spectroscopy, Mass spectroscopy, and 1-Dimensional and 2-dimensional nuclear magnetic resonance spectroscopy data. The histone deacetylase (HDAC) inhibitory and antioxidant activities of the obtained compounds were evaluated. Molecular docking experiments of the selected compound with representatives of class I (HDAC2 and HDAC8) and class II (HDAC4 and HDAC7) HDAC isoforms displayed potential isoform-selective HDAC inhibitors. Molecular docking data showed consistent results to the in vitro experiments with the highest potency against HDAC8. The docking studies suggested that the phenolic and carbonyl group can be favorably accommodated at the gorge region of the binding site. Furthermore, the phenolic groups also acted as major roles for antioxidant activities.