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Soutenance de Yeraldinne Carrasco

Physical properties of R-loops and viral capsids: a single-molecule approach based on AFM high resolution imaging and nano-indentation
When Apr 06, 2021
from 10:00 to 12:00
Where Salle des thèses
Contact Name Yeraldinne Carrasco
Attendees Yeraldinne Carrasco
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By combining high-resolution AFM images and single-molecule nanomechanical measurements, we study two different biological objects physical properties.

R-loops are hybrid DNA/RNA structures that arise from the DNA transcription process. The RNA hybridises the template DNA strand by Watson-Crick interactions, while the coding DNA strand remains single-stranded. The structures of the R-loops have been associated with phenotypes of genomic instability in vivo. We characterise the conformation of these structures generated in vitro using AFM images. We show that these R-loops, generated for different genes, differ in their architecture by analysing quantitative physical parameters. We conclude that the coding DNA strand organisation is a fundamental characteristic to form a compact hybrid object, which could then generate replication-dependent DNA breaks.

We study two viral capsids physical properties, the AAV vector and the Hepatitis B capsid, related to their disassembly. By combining mechanical response and imaging measurement in a liquid medium using AFM, we obtained quantitative information on its mechanical properties. An indentation profile on the capsid shows spatial heterogeneities, whose origin is partly geometric and results from an intrinsic heterogeneity linked to the capsid organisation. We also compared the capsids mechanical properties to release its genome in vitro when induced by temperature. Finally, we study the structure of AAV inverted terminal repeats (ITRs). These ITRs adopt a functional structure that we characterise by AFM images.