Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - PlasmoSilencing (Exoribonuclease-mediated degradation of nascent RNA in Malaria Parasites: A Novel Mechanism in Virulence Gene Silencing)

Teaser

Until lately, our knowledge on malaria parasite specific factors controlling expression of genes linked to severe malaria remained unknown. Our recent ground-breaking discovery of a mechanism that is a central player in this process via a new type of RNase-mediated gene...

Summary

Until lately, our knowledge on malaria parasite specific factors controlling expression of genes linked to severe malaria remained unknown. Our recent ground-breaking discovery of a mechanism that is a central player in this process via a new type of RNase-mediated gene silencing mechanism, opens several new avenues and represents the main focus of this proposal. Malaria remains a major burden in many endemic countries and new insight into the disease process may lead to intervention strategies that could avoid the development of severe malaria.
The overall objectives of this project will add new and important conceptual findings in the field of control of gene expression in this pathogen with potential translational aspects for the treatment of severe malaria.

Work performed

So far, we have addressed the objectives defined in this project : i) the molecular mechanism of RNase II-mediated mRNA degradation, ii) the role of PfRNase II transcript levels in severe malaria, iii) the role of exoribonucleases Dis3 and Rrp6 in posttranscriptional gene regulation. For two objective we have obtained important insight that have led to 10 publications and four manuscripts that are either submitted or under revision. One of the highlights is that the PfRNase controlled ncRNA gene family acts in trans as an enhancer-like ncRNA in monoallelic gene expression. A second highlight is that PfRNase II controlled antisense RNA made from a virulence gene intron does not have the postulated role as a general activator of the var gene family. A third discovery shows, that a second type of 3’-5’ exoribonuclease (Dis3) controls mainly antisense RNA, an emerging regulator of gene transcription in malaria parasites.

Final results

In order to overcome existing hurdles, we had to develop a number of new methods for malaria parasites. A main issue is the study of multigene virulence families that are clonally variant. Here we used the dead Cas9 to target regulatory sequences common to all members. After a number of attempts we developed protocols that now work to target specific genome regions either for pull down of chromatin associated to regions of interest or to inactivate gene transcription by interfering with the Pol II and Pol III transcription. This methodology has revealed a function for the PfRNase controlled ncRNA gene family as enhancer of transcription.

Website & more info

More info: https://research.pasteur.fr/en/team/biology-of-host-parasite-interactions/.