SUMMARY OF RESEARCH

Regulation of mRNA degradation and translation in trypanosomes

All organisms adjust their gene expression program in response to changes in the environment, and this is mainly achieved by regulating transcription initiation. Post-transcriptional events such us mRNA stability or translation also play an important role in determining levels of gene expression. This is especially true in trypanosomatid protozoans. These flagellated eukaryotes exhibit complicated life cycles alternating between an invertebrate and a vertebrate, and are able to undergo drastic morphological and biochemical changes in response to different temperature, pH, nutrients and defenses they encounter within one or the other host. All these adaptations require major changes in the gene expression program of the parasite. However, trypanosomatids seem to have completely lost the ability to regulate transcription initiation by RNA polymerase II, and no developmental regulation of RNA processing has been described. Therefore, they depend almost exclusively on the regulation of mRNA decay and translation to control the expression of many genes and to allow their rapid adaptation to the new environment.

Trypanosomatid protozoa include important human and animal pathogens such us Trypanosoma cruzi (Chagas' disease), Trypanosoma brucei ssp. (sleeping sickness) or Leishmania ssp. (visceral, cutaneous and mucocutaneous leishmaniasis). Approximately 17 million people are currently infected (http://www.who.int/en/). Few drugs are available, and many are toxic or little effective. Trypanosoma brucei, the sleeping sickness parasite, has two main life forms, the bloodstream form, found in the blood and fluids of the mammal host, and the procyclic or insect form, which multiplies in the fly. Sleeping sickness is fatal unless treated. There are 60 million people at risk, and most of the 300.000-500.000 people affected will die of the disease (http://www.who.int/mediacentre/factsheets/fs259/en/). T. brucei is the parasite of choice to study trypanosomatid gene function, since there are many genetic techniques available to carry out the basic research needed to identify novel drug targets, such us RNA interference or tetracycline-regulated gene expression.

As mentioned above, the developmental regulation of gene expression at the post-transcriptional level is of paramount importance in these parasites. Indeed, T. brucei cell growth is inhibited upon inappropriate expression of mRNAs in the ?wrong? life form, or when heterologous regulatory RNA-binding proteins are expressed in T. brucei. Therefore, the analysis of the proteins involved in regulated mRNA decay/translation should be of great help to identify potential drug targets. Moreover, the apparent absence of regulation at the level of transcription initiation in trypanosomes, the similarity of mRNA degradation mechanisms to those of mammalian cells, and the facile manipulation of these parasites make T. brucei an extremely attractive model for the analysis of the post-transcriptional regulation of gene expression.

Our main goal is to identify and characterize proteins that regulate mRNA degradation and translation using a combination of RNA-affinity chromatography, mass spectrometry, RNA interference, protein over-expression, tandem-affinity purification and microarray analyses.

Since mRNA degradation/translation is of crucial importance for parasite survival, this research should be useful in the identification of new drug targets against these human pathogens and will contribute to make trypanosomes an excellent model system to study post-transcriptional regulatory mechanisms in more complex eukaryotes.

FUNDING AGENCIES LAST 5 YEARS

- Nuevas vías de control de la expresión génica en tripanosomas. PROYECTO, INTRAMURALES CSIC, Ref: 201920E114, (2019 - 2022).

PUBLICATIONS LAST 5 YEARS

-Ceballos-Pérez, G.; Rico-Jiménez, M.; Gómez-Liñán, C.; Estévez, A.M., Role of the RNA-binding protein ZC3H41 in the regulation of ribosomal protein messenger RNAs in trypanosomes, Parasites and Vectors, 2023, Vol. 16: 1-118, ARTÍCULO, Id:945890

-Fabien Guegan; K Shanmugha Rajan; Fábio Bento; Daniel Pinto-Neves; Mariana Sequeira; Natalia Gumi¿ska; Seweryn Mroczek; Andrzej Dziembowski; Smadar Cohen-Chalamish; Tirza Doniger; Beathrice Galili; Antonio M Estévez; Cedric Notredame; Shulamit Michaeli; Luisa M Figueiredo, A long noncoding RNA promotes parasite differentiation in African trypanosomes, Science Advances, 2022, Vol. 8: eabn270624-eabn2706, ARTÍCULO, Id:909271

-Claudia Gómez-Liñán; Elena Gómez-Díaz; Gloria Ceballos-Pérez; Antonio M. Estévez, The RNA-binding protein RBP33 dampens non-productive transcription in trypanosomes, Nucleic Acids Research, 2022, Vol. 50: 12251-12265, ARTÍCULO, Id:909265

-Rico-Jiménez, M.; Ceballos-Pérez, G.; Gómez-Linãn, C.; Estévez, A.M., An RNA-binding protein complex regulates the purine-dependent expression of a nucleobase transporter in trypanosomes, Nucleic Acids Research, 2021, Vol. 49: , ARTÍCULO, Id:850604

DOCTORAL THESES LAST 5 YEARS