Poster Presentation 44th Lorne Genome Conference 2023

A mechanism of mitotic telomere deprotection (#117)

Ronnie Ren Jie Low 1 , Diana Romero-Zamora 2 3 , Samuel Rogers 1 , Alexander Sobinoff 1 , Scott G Page 1 , Hilda Pickett 1 , Makoto T Hayashi 2 3 4 , Tony J Cesare 1
  1. Children's Medical Research Institute, Westmead, NSW, Australia
  2. Graduate School of Biostudies, Kyoto University, Kyoto, Japan
  3. Graduate School of Medicine, Kyoto University, Kyoto, Japan
  4. IFOM-KU Joint Research Laboratory, IFOM, Milano, MI, Italy

Prolonged mitotic arrest in humans induces a telomere-specific and ATM-dependent DNA damage response. Mitotic telomere deprotection (MTD) is telomere-length independent, requires Aurora B kinase, corresponds with TRF2 dissociation and t-loop unwinding, and promotes mitotic death1, 2. Here we set out to identify the molecular mechanism governing MTD. Recovery of the telomere interactome in mitotically arrested HeLa cells expressing TRF1-APEX2 revealed significant enrichment of chromosome passenger complex (CPC) components INCENP, Borealin, and Aurora B Kinase, as well as the BLM Holliday junction dissolves. Both the CPC and BLM complexes are recruited to the TRF1 hinge domain. We identified TRF1 is modified in the hinge domain in an Aurora B kinase-dependent manner during mitotic arrest through phosphorylation on Ser354, and Thr358. Knock-down, inactivating mutation, and/or chemical inhibition of either the CPC or the BLM/Topo3A/RMI (BTR) complex impairs MTD, as does phospho-null mutation on TRF1-S354 and/or T358. To probe how TRF2 participates in MTD we identified consensus Aurora B motifs in TRF2, which revealed S62 and S65 (S20 and 23 in the short isoform) within the basic domain. We found the TRF2 basic domain is phosphorylated during mitotic arrest in an Aurora B-dependent manner. In agreement, phospho-null mutations on TRF2-S62 and/or 65 suppressed MTD, while phosphomimetic mutations enhanced MTD. We propose a model where coordinated phosphorylation of TRF1 during mitotic arrest recruits BTR and CPC to chromosome ends.  Once localised, Aurora B modifies TRF2 which we anticipate weakens interaction between TRF2 and the telomere enabling the BTR complex to dissolve t-loops and promote MTD.  

 

References

1. Hayashi, M., Cesare, AJ, Fitzpatrick, J. et al. A telomere-dependent DNA damage checkpoint induced by prolonged mitotic arrest. Nat Struct Mol Biol 19, 387–394 (2012). doi.org:10.1038/nsmb.2245

2. Cesare AJ, Hayashi MT, Crabbe L, Karlseder J. The telomere deprotection response is functionally distinct from the genomic DNA damage response. Mol Cell. 2013 Jul 25;51(2):141-55. doi: 10.1016/j.molcel.2013.06.006.