Tony Cesare

DNA replication and Cryo-EM star Jacob Lewis is visiting @cmri.bsky.social today to present seminar. If you happen to be in Westmead, talk is 12:30 pm local time. See you there.

Hunter Meeting 2025

Excited to speak at the Hunter Meeting next week, alongside @cmri.bsky.social colleagues Pragathi Masamsetti (postdoc with Patrick Tam, proud Cesare lab alum) and Pengyi Yang (Head, Computational Systems Biology Unit). Looking forward to great science and good company.

www.huntermeeting.org.au

If you happen to be the the Oz Single Cell Conference this week in Sydney, check out @scientistkate.bsky.social's talk on Friday.

Kate is a joint postdoc w/@piptaberlay.bsky.social and will present her work on 3D Genome architecture and replication stress.

www.ozsinglecell.com

ACCM 2025! The Cesare lab will be there in force. Come join us in Melbourne for 3 days of amazing science.

I'm super excited to announce that registrations are now open for the 19th Australian Cell Cycle, DNA Repair and Telomere Workshop. Awesome international speaker line-up, with plenty of locals being invited! Book now to secure your earlybird rate. www.australiancellcycle.org

Fantastic opportunity in Melbourne.

Hosting Lee Wong from @monashuniversity.bsky.social tomorrow to present her seminar: "Onco-histone mutations in paediatric high-grade glioma: molecular mechanisms and implications for therapy." If you are around @cmri.bsky.social tomorrow at 12:30, come by for a great talk.

@genomestability.bsky.social (Andrew Deans) will be @cmri.bsky.social tomorrow to present seminar at 12:30; "The Multifaceted Role of FANCM enzyme in DNA Repair and Cancer Therapy". If you are in the area, please do come by for a great talk.

Sorry Sam and @jenniferlovesecoli.bsky.social, I am also unaware of papers/studies exploring nuclear F-actin in c. elegans. Happy to be updated if anyone knows otherwise.

*basketball... 🤦‍♂️

My and @telomerase-cmri.bsky.social’s annual attempt to bring a little bit of college baseketball culture down under.

Go Tar Heels!

Nuclear and genome dynamics underlying DNA double-strand break repair Nature Reviews Molecular Cell Biology - Changes in nuclear and genome organization promote the repair of DNA double-strand breaks and genome stability. Processes that are involved include the...

🚀 New Paper Alert! Our latest @natrevmcb.bsky.social explores how nuclear and genome organization drive DNA double-strand break repair! 🧬

📖 Free access: rdcu.be/edViW

Please 🔄 ❤️

A CPC-shelterin-BTR axis regulates mitotic telomere deprotection Nature Communications - Here the authors reveal how telomeres signal mitotic stress. A key protein network alters their structure exposing telomere ends to signal mitotic stress, ultimately...

🧵 1/10 Excited to share our latest study in @naturecomms.bsky.social
"A CPC-shelterin-BTR axis regulates mitotic telomere deprotection" t.co/VypPsLBJCR

26/Finally, the data are consistent with t-loops suppressing ATM activation by the chromosome end.

T-loops opening in a regulated and shelterin-dependent manner to signal cellular stress suggests a broader role for these chromosome end structures than previously appreciated.

25/We predict this represents a non-canonical telomere-dependent tumour suppressive activity outside the canonical ageing-dependent proliferative barriers imposed by telomere erosion.

Additionally, we found the protective functions of the TRF2 basic domain are mitosis specific.

24/What does this mean?

We now understand the pathway of MAD-telomere deprotection that contributes to 1) cell death during mitotic arrest, and 2) p53-dependent cell cycle arrest when cells escape an elongated mitosis.

23/Live imaging from both labs revealed that TRF2 mutants that suppress MAD-telomere deprotection also reduce the prevalence of mitotic arrest driven lethality. While TRF2 mutants that promote MAD-telomere deprotection enhanced mitotic death or expedited time of mitotic arrest to lethality.

22/Of note, telomeres do not rapidly truncate in MAD-telomere deprotection like they do when the TRF2 basic domain is deleted. Thus, while the TRF2 basic domain is modified to enable BTR-dependent t-loop opening, it does not allow t-loop junction cleavage, consistent with a highly regulated pathway.

21/Diana’s molecular biology was consistent with the BTR complex being requisite for MAD-telomere deprotection following TRF2 modification.

This suggested that t-loops junctions are in a double Holliday Junction configuration during mitotic arrest before resolution by BTR.

20/How does BLM fit into the story?

BLM does many things, including double Holliday Junction dissolution (dHJ) via the BTR complex. T-loops are typically drawn with strand-invasion promoting a displacement loop. However, this is conjecture, and the t-loop junction identify is unknown.

19/Ronnie's Airyscan imaging of telomere macromolecular structure following in situ trioxsalen cross-linking and chromatin spreading suggested TRF2 basic domain phosphorylation promoted the transition from looped to linear telomeres during mitotic arrest, coinciding with telomere DDR induction.

18/Critically, both labs showed that all TRF2 S62 and/or S65 phospo-null or phospho-mimetic mutants retained interphase telomere protection, indicating these residues function specifically in mitotic telomere protection. Diana & Makoto also showed that TRF1 and TRF2 mutants localized to telomeres.

17/Sam created a phosphospecific antibody against pTRF2-S65 and his biochemistry confirmed this residue was phosphorylated specifically during mitotic arrest in an AURKB-dependent fashion.

16/Within TRF2, we identified multiple AURKB consensus sites in the basic domain, the portion of TRF2 expected to protect t-loop junctions.

Diana and Ronnie’s molecular biology was consistent with TRF2-S62 and S65 phosphorylation being requisite for MAD-telomere deprotection.

15/Survivin binding to pTRF1 suggested that CPC retention at mitotically arrested telomeres may promote AURKB modification of other shelterin factors.

Because TRF2 regulates somatic t-loops, we investigated potential AURKB-dependent TRF2 phosphorylation.

14/Sam used phospho-peptides, mass spec, and biochemistry to identify that the CPC component Survivin bound to phosphorylated pTRF1. Diana’s molecular biology and live imaging confirmed that the CPC factors INCEMP and Survivin are requied for MAD-telomere deprotection.

13/Molecular biology by Diana suggested that TRF1 S354 and T358 phosphorylation were required for MAD-telomere deprotection.

Sam created a phospho-specific antibody against pTRF1-T358 and found this residue was phosphorylated specifically during mitotic arrest by AURKB.

12/In silico analysis revealed AURKB consensus sites in the TRF1 BLM binding motif. To probe these residues, Diana depleted TRF1 and complemented with mutant alleles.

To our surprise, depleting TRF1 suppressed MAD-telomere deprotection, indicating this is a shelterin dependent phenomenon!

11/To do so, Sam developed an unbiased and time resolved TRF1-APEX2 interactomics pipeline. This revealed that telomeres in mitotically arrested cells interacted with the CPC and BLM helicase. We were excited to find that BLM depletion suppressed MAD-telomere deprotection.