A novel role of small RNA pathways in regulating DNA replication in polyploid cells.

Descripción del proyecto

El papel de los ARN pequeños en la estabilidad del genoma

Se sabe que los ARN pequeños, como los microARN, desempeñan un papel fundamental en la regulación de la expresión génica. Con el apoyo de las Acciones Marie Skłodowska-Curie, el equipo del proyecto sRNAUR pretende explorar si los ARN pequeños y, en particular, los ARN asociados a Piwi (Piwi-ARN) regulan el número de copias de ADN en la «Drosophila». Hasta ahora, las pruebas indican que los Piwi-ARN protegen el genoma de la línea germinal, lo que facilita la formación de heterocromatina en las regiones de ADN repetitivo. En el proyecto se investigará si los Piwi-ARN regulan la cantidad de ADN centromérico e influyen en cómo se heredan los rasgos. Mediante el uso de técnicas avanzadas de secuenciación e imagen, se espera que en sRNAUR se descubran conocimientos nuevos sobre cómo los ARN pequeños ayudan a mantener la estabilidad del genoma.

Objetivo

Small RNA-mediated gene regulation and DNA replication are fundamental genome-regulatory pathways essential for cellular life, organismal development, and disease prevention. While small RNA pathways are known to sequence-specifically regulate DNA copy number in some unicellular animals, such connections have yet to be found in multicellular animals. With this project, I will investigate and mechanistically characterize such a potential connection in the Drosophila animal model system.
Piwi-interacting RNAs (piRNAs), a class of animal small RNAs, safeguard the germline genome against repetitive DNA proliferation by guiding repressive heterochromatin formation at target loci. In Drosophila melanogaster ovarian nurse cells, heterochromatic (peri)centromeric DNA repeats undergo selective local suppression of DNA replication thus lowering their relative copy number. Interestingly, abundant piRNAs able to target to these 'underreplicated' regions have been found, yet the potential functional interactions between small RNA genome defense and DNA replication remain unexplored. With this project, I will bridge this gap by investigating the role of satellite piRNAs in Drosophila melanogaster, focusing on the interplay between regulated DNA replication and small RNA genome defense. Two interconnected hypotheses will be examined: (1) piRNA-directed heterochromatin formation regulates centromeric DNA copy number, and (2) piRNA-regulated heterochromatin sinks alter epigenetic inheritance. To do so, I will apply advanced sequencing- and imaging-based methods for DNA copy number quantification and leverage the powerful Drosophila genetics to uncover underlying molecular mechanisms.
In sum, my investigation of small RNA-based regulation of DNA replication holds the promise to reveal a new paradigm in animal genome regulation and to provide deeper insights into the mechanisms regulating genome stability and the role of piRNAs in maintaining it.