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Anne Katrine Wrist Simonsen:
ZGRF1 Contributes to DNA Repair, Secondary DNA Structure Regulation, and Transcriptional Alteration

Date: 14-11-2022    Supervisor: Michael Lisby & Vibe Østergaard



Maintaining genome integrity is essential to life. DNA encodes proteins that take care of most functions in the cell, and correct expression of proteins is important. Helicases remodel nucleic acid structures and play important roles in DNA replication, repair, and transcription. DNA secondary structures such as R-loops and G-quadruplexes can contribute to genomic instability but are also involved in the regulation of transcription and replication.

In this work, I contribute to a genetical and cell biological characterization of the novel human helicase ZGRF1. It is shown that ZGRF1 is a 5’-3’ DNA helicase with the ability to unwind D-loops and migrate branched DNA structures. ZGRF1 localizes to the nucleus and promotes homologous recombination, and ZGRF1-/- cells are sensitive to the replication-blocking agents Mitomycin C and Camptothecin.

Moreover, I present an NMR structure and putative interactors of the ZGRF1 N-terminal DUF2439 domain. After the initial characterization, I elucidate the ability of ZGRF1 to regulate secondary DNA structures and affect transcription. ZGRF1 is shown to dissolve R-loops in vitro, and transcriptional levels of 142 genes are reported upregulated while 135 genes are downregulated in parental cells compared to ZGRF1-/- U2OS cells.

Transcriptional levels of E2F8, PDE3B, LDHC, PASD1, and ACCS are more than 100-fold higher in the parental cells compared ZGRF1-/- cells where transcription of these genes is almost abolished. Promoter regions of genes with altered transcription levels in ZGRF1-/- cells are enriched for several motifs with a predicted potential for forming G-quadruplexes.

The results suggest that ZGRF1 might contribute to regulating transcription through secondary DNA structures in the promoter regions. Besides, the transcriptional alteration of E2F8, PDE3B, and LDHC points towards cancer, obesity, and male fertility as interesting topics of research when further investigating the function of ZGRF1.