Biology subjects

Esposito, M.

Publications and source records attributed to Esposito, M..

21 records · Page 2Linked to original sources

bioRxiv2019

Surface association induces cytotoxic alkyl-quinolones in Pseudomonas aeruginosa

Surface attachment, an early step in the colonization of multiple host environments, activates the virulence of the human pathogen P. aeruginosa. However, the signaling pathways and downstream toxins specifically induced by surface association to stimulate P. aeruginosa virulence are not fully understood. Here, we demonstrate that alkyl-quinolone (AQ) secondary metabolites are rapidly induced upon surface association and represent a major class of surface-dependent cytotoxins. AQ cytotoxicity is direct and independent of other AQ functions like quorum sensing or PQS-specific activities like iron sequestration. Furthermore, the regulation of AQ production can explain the surface-dependent virulence regulation of the quorum sensing receptor, LasR, and the pilin-associated candidate mechanosensor, PilY1. PilY1 regulates surface-induced AQ production by repressing the AlgR-AlgZ two-component system. AQs also contribute to the known cytotoxicity of secreted outer membrane vesicles. These findings collectively explain previously mysterious aspects of virulence regulation and provide new avenues for the development of anti-infectives.

microbiology↗

bioRxiv2018

PLZF limits enhancer activity during hematopoietic progenitor aging

PLZF (promyelocytic leukemia zinc finger) is a transcription factor acting as a global regulator of hematopoietic commitment. PLZF displays an epigenetic specificity by recruiting chromatin-modifying factors but little is known about its role in remodeling chromatin of cells committed towards a given specific hematopoietic lineage. In murine myeloid progenitors, we decipher a new role for PLZF in restraining active genes and enhancers by targeting acetylated lysine 27 of Histone H3 (H3K27ac). Functional analyses reveal that active enhancers bound by PLZF are involved in biological processes related to metabolism and associated with hematopoietic aging. Comparing the epigenome of young and old myeloid progenitors, we reveal that H3K27ac variation at active enhancers is a hallmark of hematopoietic aging. Taken together, these data suggest that PLZF, associated with active enhancers, appears to restrain their activity as an epigenetic gatekeeper of hematopoietic aging.

molecular biology↗

bioRxiv2018

Non-synonymous to synonymous substitutions suggest that orthologs tend to keep their functions, while paralogs are a source of functional novelty

Orthologs diverge after lineage separation events and paralogs after gene duplications. Thus, orthologs are expected to remain more functionally coherent across lineages, while paralogs have been proposed as a source of new functions. Because protein functional divergence follows from non-synonymous substitutions, we performed an analysis based on the ratio of non-synonymous to synonymous substitutions (dN/dS), as proxy for functional divergence. We used five working definitions of orthology, including reciprocal best hits (RBH), among other definitions based on network analyses and clustering. The results showed that orthologs, by all definitions tested, had values of dN/dS noticeably lower than those of paralogs, suggesting that, as a group, orthologs tend to be more functionally stable than paralogs. The differences in dN/dS ratios remained suggesting the functional stability of orthologs after eliminating gene comparisons with potential problems, such as genes with high codon usage biases, low coverage of either of the aligned sequences, or sequences with very high similarities. Separation by percent identity of the encoded proteins showed that the differences between the dN/dS ratios of orthologs and paralogs were more evident at high sequence identity, less so as identity dropped. While the last results partially explained the differences between dN/dS ratios of the two groups as being related to differences in protein identity, they also suggested that paralogs undergo functional divergence relatively early after duplication. Our analyses indicate that choosing orthologs as probably functionally coherent remains the right approach in comparative genomics.

evolutionary biology↗