Summary We report the target, biochemical basis, and structural basis of inhibition of bacterial RNA polymerase (RNAP) by the α-pyrone antibiotic myxopyronin (Myx). We show that Myx interacts with the RNAP “switch region,” the hinge that mediates opening and closing of the RNAP active-center cleft. We show that Myx prevents interaction of RNAP with promoter DNA. We present a crystal structure that defines contacts between Myx and RNAP and defines effects of Myx on RNAP conformation. We propose that Myx functions by preventing opening of the RNAP active-center cleft to permit entry of DNA during transcription initiation (“hinge jamming”). We establish further that the structurally related α-pyrone antibiotic corallopyronin and the structurally unrelated macrocyclic-lactone antibiotic ripostatin function through the same target and same mechanism. The RNAP switch region is an attractive target for identification of new broad-spectrum antibacterial therapeutic agents.

Pre-mRNA splicing is regulated through combinatorial activity of RNA motifs including splice sites and splicing regulatory elements (SREs). Here, we show that the activity of the G-run class of SREs is ∼4-fold higher when adjacent to intermediate strength 5'ss relative to weak 5'ss, and ∼1.3-fold higher relative to strong 5'ss. This dependence on 5'ss strength was observed in splicing reporters and in global microarray and mRNA-Seq analyses of splicing changes following RNAi against heterogeneous nuclear ribonucleoprotein (hnRNP) H, which crosslinked to G-runs adjacent to many regulated exons. An exon’s responsiveness to changes in hnRNP H levels therefore depends in a complex way on G-run abundance and 5'ss strength, and other splicing factors may function similarly. This pattern of activity enables G-runs and hnRNP H to buffer the effects of 5'ss mutations, augmenting the frequency of 5'ss polymorphism and the evolution of new splicing patterns.

Health inequities have long defined health and the healthcare system in the USA. The clinical and research capacity across the USA is unparalleled, yet compared to other high and even some middle-income countries, the average health indicators of the population remain suboptimal in 2020, a finding at least in part explained by inequity in healthcare access. In this context, COVID-19 has rapidly emerged as a major threat to the public’s health. While it was initially thought that severe acute respiratory syndrome coronavirus 2 would be the great equaliser as it would not discriminate, it is clear that COVID-19 incidence and mortality have rapidly reinforced health disparities drawn by historical and contemporary inequities. Here, we synthesise the data highlighting specific risks among particular marginalised and under-resourced communities including those in jails, prisons and detention centers, immigrants and the undocumented, people with disabilities and people experiencing homelessness across the USA. The drivers of these disparities are pervasive structural risks including limited access to preventive services, inability to comply with physical distancing recommendations, underlying health disparities and intersecting stigmas particularly affecting racial and ethnic minorities across the country, including African Americans, Latinx Americans and Native Americans. Advancing the COVID-19 response, saving lives and restarting the economy necessitate rapidly addressing these inequities rather than ignoring and even reinforcing them.