In partial fulfillment of the requirements for the degree of

Master of Science in Biology

in the

School of Biological Sciences

Yixun Tan

Will defend his thesis

“Role of RNase H1 in RNA-mediated End Joining Repair”

12 JANUARY 2026

14:30

https://gatech.zoom.us/j/91594268291?pwd=Lv4EbpeocuTRDSbmb6ZIjWXssDS0Sz.1

Thesis Advisor:

Dr. Francesca Storici

School of Biological Sciences

Georgia Institute of Technology

Committee Members:

Dr. Yury O. Chernoff

School of Biological Sciences

Georgia Institute of Technology

 Dr. Andrew McShan

School of Chemistry & Biochemistry

Georgia Institute of Technology

Abstract: RNA has increasingly been recognized as an active participant in the repair of DNA double-strand breaks (DSBs), extending the classical DNA-centric view,In multiple organisms, transcript RNA and RNA–DNA hybrids have been shown to influence repair efficiency and pathway choice, yet the regulatory mechanisms governing RNA-mediated end joining at chromosomal breaks remain incompletely understood. RNase H1, a conserved enzyme that selectively degrades the RNA strand of RNA–DNA hybrids, represents a key factor linking RNA metabolism to genome maintenance.

This thesis investigates the role of RNase H1 in RNA-mediated end-joining repair using a chromosomal reporter system in Saccharomyces cerevisiae. Antisense and branchΔ intron-containing constructs were integrated into the yeast genome to generate spliced and non-spliced RNA species in a defined chromosomal context. These constructs were analyzed in parallel wild-type and rnh1Δ backgrounds, allowing direct assessment of how RNase H1 status influences RNA processing and repair outcomes. A genetically controlled strain panel was generated through targeted deletion and restoration of the endogenous RNH1 locus using the delitto perfetto strategy.