SymbNET Online Seminar Series

This Seminar Series is open and free of charge, but registration is required.
Info: https://symbnet.eu/agenda/seminar-series-22-september/

15h

Speaker: Ute Hentschel Humeida

Affiliation: GEOMAR, Germany

Title: A Symbiont phage protein aids in eukaryote immune evasion.

Abstract:

Phages are increasingly recognized as important members of host-associated microbiomes. While recent studies have revealed vast genomic diversity in the virosphere, the new frontier is to understand how phages may affect higher order processes, such as in the context of host-microbe interactions. Here, we combine viral metagenomics with functional assays to investigate the interplay between phages, bacterial symbionts and marine sponges. We find that sponges, although massively filtering seawater, harbour species-specific and even individually unique viral signatures that are taxonomically distinct from other environments. We further discover a symbiont phage-encoded ankyrin domain-containing protein which is widely spread in phages of many host-associated contexts including human. The ankyrin protein (ANKp) modulates the eukaryotic immune response against bacteria as confirmed in macrophage infection assays. We predict that the role of ANKp in nature is to facilitate co-existence in the tripartite interplay between phages, symbionts, and sponges and possibly many other host-microbe associations.

15h30

Speaker: Luísa Figueiredo

Affiliation: IMM, Portugal

Title: Antigenic variation in African trypanosomes: small RNA modifications, big impact.

Abstract:

RNA modifications are important regulators of gene expression. In Trypanosoma brucei, transcription is polycistronic and thus most regulation happens post-transcriptionally. N6-methyladenosine (m6A) has been detected in this parasite, but its function remained unknown. Recently we found that m6A is enriched in 342 transcripts using RNA immunoprecipitation, with an enrichment in transcripts encoding variant surface glycoproteins (VSGs). Approximately 50% of the m6A is located in the poly(A) tail of the actively expressed VSG transcripts. m6A residues are removed from the VSG poly(A) tail before deadenylation and mRNA degradation. Computational analysis revealed an association between m6A in the poly(A) tail and a 16-mer motif in the 3′ untranslated region of VSG genes. Using genetic tools, we show that the 16-mer motif acts as a cis-acting motif that is required for inclusion of m6A in the poly(A) tail. Removal of this motif from the 3′ untranslated region of VSG genes results in poly(A) tails lacking m6A, rapid deadenylation and mRNA degradation. To our knowledge, this is the first identification of an RNA modification in the poly(A) tail of any eukaryote, uncovering a post-transcriptional mechanism of gene regulation.