Biology subjects

Erkelens, A. M.

Publications and source records attributed to Erkelens, A. M..

3 recordsLinked to original sources

bioRxiv2021

Novel anti-repression mechanism of H-NS proteins by a phage "early protein".

H-NS family proteins, bacterial xenogeneic silencers, play central roles in genome organization and in the regulation of foreign genes. It is thought that gene repression is directly dependent on the DNA binding modes of H-NS family proteins. These proteins form lateral protofilaments along DNA. Under specific environmental conditions they switch to bridging two DNA duplexes. This switching is a direct effect of environmental conditions on electrostatic interactions between the oppositely charged DNA binding and N-terminal domains of H-NS proteins. The Pseudomonas lytic phage LUZ24 encodes the early protein gp4, which modulates the DNA binding and function of the H-NS family protein MvaT of Pseudomonas aeruginosa. However, the mechanism by which gp4 modulates MvaT activity remains elusive. In this study, we show that gp4 specifically interferes with the formation and stability of the bridged MvaT-DNA complex. Structural investigations suggest that gp4 acts as an "electrostatic zipper" between the oppositely charged domains of MvaT protomers, and stabilizes a structure resembling their "half-open" conformation, resulting in relief of gene silencing and adverse effects on P. aeruginosa growth. The ability to control H-NS conformation and thereby its impact on global gene regulation and growth might open new avenues to fight Pseudomonas multidrug resistance.

biochemistry↗

bioRxiv2021

The nucleoid-associated protein Gbn binds to GATC sequences and affects sporulation and antibiotic production in Streptomyces

Bacterial chromosome structure is organized by a diverse group of proteins collectively referred to as nucleoid-associated proteins (NAPs). Many NAPs have been well studied in Streptomyces, including Lsr2, HupA, HupS, and sIHF. Here, we show that SCO1839 represents a novel family of Actinobacteria NAPs and recognizes a consensus sequence consisting of GATC followed by (A/T)T. The protein was designated Gbn for GATC-binding NAP. Deletion of gbn led to alterations in development and antibiotic production in Streptomyces coelicolor. Chromatin immunoprecipitation sequencing (ChIP-Seq) detected more than 2800 binding regions, encompassing some 3600 GATCWT motifs, which comprise 55% of all such motifs in the S. coelicolor genome. DNA binding of Gbn in vitro increased DNA stiffness but not compaction, suggesting a role in regulation rather than chromosome organization. Transcriptomics analysis showed that Gbn binding generally leads to reduced gene expression. The DNA binding profiles were nearly identical between vegetative and aerial growth. Exceptions are SCO1311 and SCOt32, for a tRNA editing enzyme and a tRNA that recognises the rare leucine codon CUA, respectively, which nearly exclusively bound during vegetative growth. Taken together, our data show that Gbn is a highly pleiotropic NAP that impacts growth and development in streptomycetes. IMPORTANCEA large part of the chemical space of bioactive natural products is derived from Actinobacteria. Many of the biosynthetic gene clusters for these compounds are cryptic, in others words, they are expressed in nature but not in the laboratory. Understanding the global regulatory networks that control gene expression is key to the development of approaches to activate this biosynthetic potential. Chromosome structure has a major impact on the control of gene expression. In bacteria, the organization of chromosome structure is mediated by a diverse group of proteins referred to collectively as nucleoid-associated proteins (NAPs), which play an important role in the control of gene expression, nucleoid structure and DNA repair. We here present the discovery of a novel and extremely pleiotropic NAP, which we refer to as Gbn. Gbn is a sporulation-specific protein that occurs only in the Actinobacteria and binds to GATC sequences, with a subtle but broad effect on global gene expression. The discovery of Gbn is a new step towards better understanding of how gene expression and chromosome structure is governed in antibiotic-producing streptomycetes.

molecular biology↗

bioRxiv2019

The B. subtilis Rok protein compacts and organizes DNA by bridging

Rok from Bacillus subtilis is an abundant DNA binding protein similar in function to H-NS-like proteins found in many proteobacteria. Rok binds across the genome with a preference for A/T rich DNA. Such DNA often contains genes of foreign origin that are silenced due to Rok binding. Rok also has been implied in global organization of the B. subtilis genome. However, how Rok binds to DNA and how it represses transcription is unclear. Also, it is unknown whether Rok-mediated gene repression can be induced or relieved following changes in physico-chemical conditions, as noted for H-NS-like proteins. Here we investigate the DNA binding properties of Rok and determine the effects of physico-chemical conditions on these properties. We demonstrate that Rok is a DNA bridging protein similar to H-NS like proteins from E. coli (H-NS), Pseudomonas sp. (MvaT) and Mycobacteria (Lsr2). Strikingly, unlike these proteins, the ability of Rok to bridge DNA is not affected by changes in physico-chemical conditions. Not being a direct sensor of such changes sets Rok apart from other H-NS like proteins. It implies the existence of other (protein-mediated) mechanisms to relieve Rok-mediated gene silencing in response to changes in environmental conditions.

molecular biology↗