Biology subjects

Brewer, J. J.

Publications and source records attributed to Brewer, J. J..

3 recordsLinked to original sources

bioRxiv2024

RapA opens the RNA polymerase clamp to disrupt post-termination complexes and prevent cytotoxic R-loop formation

Following transcript release during intrinsic termination, Escherichia coli RNA polymerase (RNAP) often remains associated with DNA in a post-termination complex (PTC). RNAPs in PTCs are removed from the DNA by the Swi2/Snf2 ATPase RapA. Here, we determined PTC structures on negatively-supercoiled DNA as well as of RapA engaged to dislodge the PTC. We found that core RNAP in the PTC can unwind DNA and initiate RNA synthesis but is prone to producing R-loops. We show that RapA helps control cytotoxic R-loop formation in vivo, likely by disrupting PTCs. Nucleotide binding to RapA triggers a conformational change that opens the RNAP clamp, allowing DNA in the RNAP cleft to reanneal and dissociate. We suggest that analagous ATPases acting on PTCs to suppress transcriptional noise and R-loop formation may be widespread. These results hold significance for the bacterial transcription cycle and highlight a role for RapA in maintaining genome stability.

biophysics↗

bioRxiv2022

Structural and functional basis of the universal transcription factor NusG pro-pausing activity in Mycobacterium tuberculosis

Transcriptional pauses mediate regulation of RNA biogenesis. DNA-encoded pause signals trigger elemental pausing by stabilizing a half-translocated (RNA-not-DNA) state and by promoting RNAP swiveling that other factors can enhance. The universal transcription factor NusG (Spt5 in eukaryotes and archaea) N-terminal domain (NGN) modulates pausing through contacts to RNAP and DNA. Pro-pausing NusGs (e.g., Bacillus subtilis) enhance some pauses whereas anti-pausing NusGs (e.g., Escherichia coli) suppress some pauses. Little is known about pausing and NusG in the human pathogen Mycobacterium tuberculosis (Mtb). Using biochemistry and cryo-electron microscopy, we show that MtbNusG is a pro-pausing NusG that captures paused, swiveled RNAP by contacts to the RNAP protrusion and to a nontemplate strand-DNA wedge inserted between the NGN and the RNAP gate loop. On the other hand, we find that anti-pausing E. coli NGN contacts the RNAP gate loop to inhibit swiveling and pausing of MtbRNAP. Using CRISPR-mediated mycobacterial genetics, we show that a pro-pausing NGN is required to support robust mycobacterial growth. Our results define an essential function of NusG in mycobacteria and the structural basis of pro-vs. anti-pausing NusG activity with broad implications for NusG function in all domains of life.

molecular biology↗

bioRxiv2020

DIP/Dpr interactions and the evolutionary design of specificity in protein families

Differential binding affinities among closely related protein family members underlie many biological phenomena, including cell-cell recognition. Drosophila DIP and Dpr proteins mediate neuronal targeting in the fly through highly specific protein-protein interactions. We show here that DIPs/Dprs segregate into seven specificity subgroups defined by binding preferences between their DIP and Dpr members. We then describe a novel sequence-, structure- and energy-based computational approach, combined with experimental binding affinity measurements, to reveal how specificity is coded on the canonical DIP/Dpr interface. We show that binding specificity of DIP/Dpr subgroups is controlled by "negative constraints", which interfere with binding. To achieve specificity, each subgroup utilizes a different combination of negative constraints, which are broadly distributed and cover the majority of the protein-protein interface. We discuss the structural origins of negative constraints, and potential general implications for the evolutionary origins of binding specificity in multi-protein families.

biophysics↗