Poster Presentation 41st Lorne Genome Conference 2020

GCNA interacts with Spartan and Topoisomerase II to regulate genome stability  (#172)

Gregory Davis 1 , Gregory A Dokshin 2 , Ashley D Sawle 3 , Matthew D Eldridge 3 , Taylin E Gourley 1 , Katherine A Romer 4 5 , Luke W Molesworth 1 , Hannah R Tatnell 1 , Ahmet R Ozturk 2 , Dirk G de Rooij 5 6 , Gregory J Hannon 3 7 , David C Page 5 6 , Craig C Mello 2 8 , Michelle A Carmell 2 5 7
  1. School of Health and Life Sciences, Federation University, Churchill, Victoria, Australia
  2. RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester , MA, USA
  3. Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
  4. Computational and Systems Biology Program, Massachusetts Institute of Technology, Cambridge, MA, USA
  5. Whitehead Institute, Cambridge, MA, USA
  6. Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA, USA
  7. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
  8. Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA

Germ cell chromosomes are subjected to continuous activity that threatens their genomic integrity, including meiotic double stranded DNA breaks, homologous recombination, and a large exchange of histones. Due to this, genomic surveillance and repair mechanisms are vital in germ cells and ensure the survival of a species. While several forms of DNA damage repair maintain genomic homeostasis, the DNA-protein crosslink repair pathway (DPC) removes proteins that are inappropriately covalently crosslinked to DNA. This can occur from exposure to ionizing radiation, chemical crosslinkers, and trapped enzymatic intermediates. Topoisomerases modify DNA and are required for multiple aspects of chromosome biology, including initiating single stranded and double stranded DNA breaks via TOP-1 and TOP-2 respectively. Due to this, topoisomerase associated DPCs occur frequently and need to be resolved to prevent genomic lesions and mutations from occurring. TOP-1 DPCs are amended during S phase via co-expression of the highly conserved eukaryotic protein, Spartan/DVC-1. However, TOP-2 is highly expressed in the G2/M phase, and an understanding of how TOP-2 DPC repair is facilitated remains unknown. Using C. elegans and mouse embryonic stem cells, we show that the highly conserved germline and embryo enriched protein, GCNA-1, physically interacts and colocalises with TOP-2 on condensed chromosomes during M phase. In addition to this, CGNA-1 mutants are hyper sensitive to inhibition of TOP-2, but not TOP-1, suggesting a role for GCNA-1 in processing TOP-2 DPCs. Collectively, this study shows that GCNA-1 is a highly conserved protein that is essential for maintaining germline and embryonic genomic integrity.