So, L. | bioRxiv Science

bioRxiv2023

Discovery, Characterization, and Bioactivity of the Achromonodins: Lasso Peptides Encoded by Achromobacter

Through genome mining efforts, we discovered two lasso peptide biosynthetic gene clusters (BGCs) within two different species of Achromobacter, a genus that contains pathogenic organisms that can infect patients with cystic fibrosis. Using gene-refactored BGCs in E. coli, we heterologously expressed two lasso peptides, which we named achromonodin-1 and achromonodin-2. Achromonodin-1 is naturally encoded by certain isolates from the sputum of patients with cystic fibrosis. We solve the NMR structure of achromonodin-1, demonstrating that it is a threaded lasso peptide with a large loop and short tail structure, reminiscent of previously characterized lasso peptides that inhibit RNA polymerase (RNAP). We then show that achromonodin-1 inhibits RNAP in vitro and has potent but narrow-spectrum activity towards Achromobacter pulmonis, another isolate from the sputum of a cystic fibrosis patient. Our efforts expand the repertoire of antimicrobial lasso peptides and provide insights into how Achromobacter isolates from certain ecological niches may interact with each other.

biochemistry↗

bioRxiv2021

Active Translation Control of CD4 T Cell Activation by Regulatory T Cells

Increased protein synthesis is a hallmark of lymphocyte activation. Regulatory T cells (Tregs) suppress the activation and subsequent effector functions of CD4 effector T cells (Teffs). However, molecular mechanisms that enforce Treg-mediated suppression in CD4 Teff are not fully clear. Control of CD4 Teff activation by Tregs has largely been defined at the transcriptional level, which does not reflect changes in post-transcriptional control. We found that Tregs suppressed activation-induced global protein synthesis in CD4 Teffs prior to cell division. We analyzed genome-wide changes in the transcriptome and translatome of activated CD4 Teffs using two independent approaches. We show that mRNAs encoding for the protein synthesis machinery are regulated at the level of translation in activated Teffs. Strikingly, Tregs suppressed global protein synthesis of CD4 Teffs by specifically inhibiting mRNAs of the translation machinery at the level of mTORC1-mediated translation control. Lastly, we found that the RNA helicase eIF4A inhibitor rocaglamide A (RocA) can suppress CD4 Teff activation in vitro to alleviate inflammatory CD4 Teff activation caused by acute Treg depletion in vivo. These data provide evidence that peripheral tolerance is enforced by Tregs through mRNA translational control in CD4 Teffs. Therefore, therapeutic targeting of the protein synthesis machinery can be expected to mitigate inflammatory responses invoked by Treg loss of function.

immunology↗