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Altering translation allows E. coli to overcome chemically stabilized G-quadruplexes

ABSTRACT: G-quadruplex (G4) structures can form in guanine-rich stretches of DNA or RNA and have been found to modulate a variety of cellular processes including replication, transcription, and translation. Most studies on the cellular roles of G4s have focused on eukaryotic systems, with far fewer probing G4s in bacteria. We utilized a chemical-genetic approach to identify genes in Escherichia coli that are important for growth in conditions that stabilize G4s. Our screens reveal translation elongation to be a key process that is impacted by G4 stabilization. Reducing levels of elongation factor Tu or slowing translation elongation with chloramphenicol suppress the effects of G4 stabilization. In contrast, downregulating the levels of certain essential translation termination or ribosome recycling proteins is detrimental to growth in G4-stabilizing conditions. Proteomic and transcriptomic analyses demonstrate that ribosome assembly factors and other proteins involved in translation generally are less abundantly expressed under G4-stabilizing conditions. Taken together, the results suggest that RNA G4s present barriers to E. coli growth in G4-stabilizing conditions and reducing the rate of translation can help compensate for G4-related stress.

ORGANISM(S): Escherichia coli

PROVIDER: GSE271718 | GEO | 2024/08/19

REPOSITORIES: GEO

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Project description:DNA secondary structures are important for fundamental genome functions such as transcription and replication1. The G-quadruplex (G4) structural motif has been linked to gene regulation2,3 and genome instability4,5 and may be important to cancer development and other diseases6-8. Recently, ~700,000 discrete G4s have been observed in naked human single-stranded genomic DNA using G4-seq, a high-throughput sequencing technique that detects structural features in vitro.9 It is of vital importance to investigate G4 structures within an endogenous chromatin context, which until now remained elusive10,11. Herein, we address this via the development of G4 ChIP-seq, an antibody-based G4 chromatin immunoprecipitation and high-throughput sequencing approach. We identified ~10,000 endogenous G4 structures and show that G4s are predominantly seen in regulatory, nucleosome-depleted, chromatin regions. G4s were enriched in the promoters and 5âUTR regions of highly transcribed genes, particularly in genes related to cancer and in somatic copy number amplifications, such as MYC. Reorganization of the chromatin landscape using a histone deacetylase inhibitor, resulted in de novo G4 formation in new and more prominent regulatory, nucleosome-depleted regions associated with increased transcriptional output. Our findings suggest a striking relationship between promoter nucleosome-depleted regions, G4 formation and elevated transcriptional activity. Comparison between normal human epidermal keratinocytes and their immortalized counterparts revealed a ï¾7-fold greater G4 abundance in immortalized cells, of which 80 % were found in regulatory, nucleosome-depleted regions common to both cell types. Consequently, cells exhibiting more G4s displayed significantly increased transcriptional output and were more sensitive to growth inhibition by a small molecule G4 ligand. Overall, our results provide new mechanistic insights into where and when DNA adopts G4 structure in vivo. Our findings show for the first time that regulatory, nucleosome-depleted chromatin and transcriptional states predominantly shape the endogenous G4 DNA landscape. Two cell lines, treated with entinostat or untreated, analyzed to detect gene expression differences, presence of G-Qudruplexes and chromatin state. Each combination of conditions replicated in duplicates or triplicates.

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Altering translation allows E. coli to overcome chemically stabilized G-quadruplexes

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