Best Poster Awards: Friend or Foe — Transcription and RNA Meet DNA Replication and Repair

During the second virtual EMBO | EMBL Symposium of the year three scientists were awarded a prize for their scientific poster. In this blog, we present the winners and their research.

Friend or Foe attracted 336 participants worldwide, discussing transcription and RNA and DNA replication and repair in live sessions and panel discussions. Three poster session rounds gave the opportunity for participants to view 72 digital posters and interact with the poster presenters.

After the sessions, a voting round followed and three presenters were distinguished with a best poster award by popular vote.

  1. Gianluca Sigismondo of the German Cancer Research Center in Heidelberg, Germany.
  2. Tycho Mevissen, Howard Hughes Medical Institute and Harvard Medical School, USA
  3. Sara Luzzi, Newcastle University, UK

Read our blog on how to create a prize-winning digital poster.

Chromatin dynamics during DNA repair investigated via chromatin-directed proteomics

A portrait picture of scientist Gianluca Sigismondo
Gianluca Sigismondo, German Cancer Research Center, Germany. PHOTO: Gianluca Sigismondo

Poster presenter: Gianluca Sigismondo

Authors: Gianluca Sigismondo, Lavinia Arseni, Jeroen Krijgsveld

DNA lesions predispose to genomic instability, a hallmark of cancer; therefore cells have evolved repair pathways to solve those harmful insults.

Double-strand breaks (DSBs) represent the most lethal DNA damage first marked by the phosphorylation of the histone H2A.X (γH2A.X) which triggers the recruitment of sensor proteins belonging to either the error-prone non-homologous end joining (NHEJ) or the efficient homologous recombination (HR) pathway.

It is now established that chromatin has an active role also in DNA repair, thus its characterization at DSB repair foci is essential to better understand the coordinate action of the repair mechanisms and to identify novel players participating in tumor-associated apoptotic resistance and cell survival.

Here we dissect chromatin changes upon exposure to ionizing radiations through multiple proteomics-based approaches. We applied the Selective Isolation of Chromatin-Associated Protein strategy (ChIP-SICAP; Rafiee, 2016) to investigate the interactors of core NHEJ, HR proteins and γH2A.X while bound to the DNA or in the chromatin soluble fraction.

Through a click chemistry-assisted procedure we profiled the configuration of DNA-bound proteins during DSBs repair; finally we analyzed the histone post-translational modifications (hPTMs) cross-talk at mono-nucleosomes marked by γH2A.X.

Our integrated analysis identified the dynamics of expected chromatin determinants during the DNA repair and interestingly suggested the role for new candidates specifically enriched upon DSB formation.

Validation experiments based on monitoring of DSB foci formation and resolution in AID-DIvA cells proficient or knock-down cells provided evidence of a role for novel candidates in DNA repair. FACS-based analysis of Traffic-light Reporter (TLR) isogenic cells upon silencing of proteins identified by MS characterized their functional role in NHEJ, HR or pathway choice. Furthermore, we defined hPTMs associated with γH2A.X-marked mono-nucleosomes and their dynamics during DSB resolution.

This analysis corroborated expected enrichments (e.g. H4K20me1/me2) and provided insights on new modifications specifically enriched at γH2A.X-nucleosomes.

Chromatin dynamics during DNA repair investigated via chromatin-directed proteomics

Towards transcription-coupled DNA repair in Xenopus egg extract

Poster presenter: Tycho Mevissen

A portrait of scientist Tycho Mevissen
Tycho Mevissen, Harvard Medical School, USA. PHOTO: Tycho Mevissen

This poster and abstract contain unpublished data and are not available at this moment.

Tycho Mevissen is a postdoctoral research fellow in Johannes Walter’s lab at Harvard Medical School. He had completed his PhD with David Komander at the MRC Laboratory of Molecular Biology in Cambridge, UK, where he used structural and biochemical tools to elucidate the intricate mechanisms of enzymes in the ubiquitin system, in particular deubiquitinases (DUBs).

His current research interests in the Walter lab revolve around molecular mechanisms at the intersection of DNA transcription, replication and repair.

In particular, he is interested in understanding how elongating RNA polymerase II deals with various types of obstacles – including different DNA lesions – during transcription elongation. To study this, he uses Xenopus egg extract, which is a powerful cell-free system that has been successfully used to recapitulate a wide range of cellular DNA repair pathways.

RBMX enables productive RNA processing of ultra long exons important for genome stability

A portrait picture of scientist Sara Luzzi
Sara Luzzi, Newcastle University, UK. PHOTO: Sara Luzzi

Poster presenter: Sara Luzzi

Authors: Sara Luzzi, Gerald Hysenaj, Chileleko Siachisumo, Kathleen Cheung, Matthew Gazzara, Katherine James, Caroline Dalgliesh, Mahsa Kheirollahi Chadegani, Ingrid Ehrmann, Graham R Smith, Simon J Cockell, Jennifer Munkley, Yoseph Barash, and David J Elliott.

The nuclear RNA binding protein RBMX has a direct role in genome repair and is required for expression of the tumour suppressor BRCA2. Here we report that RBMX controls RNA processing of key genes involved in genome maintenance in breast cancer cells.

Our data demonstrate that RBMX represses a premature polyadenylation site that would truncate BRCA2 protein, and is essential for full-length mRNA expression from other genes important for genome stability. These include ETAA1, which encodes for a key replication fork protein, where RBMX and its protein interaction partner Tra2ß efficiently suppress a weak splice site to enable ETAA1 protein expression.

More generally, we propose that RBMX facilitates correct inclusion of unusually long exons within mature mRNAs by repressing cryptic RNA processing. Our data provide new molecular insights explaining the role of RBMX in DNA repair and genome maintenance.

Poster RBMX enables productive RNA processing of ultra-long exons important for genome stability

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Best Poster Awards – In Situ Structural Biology Workshop

The EMBO Workshop: In Situ Structural Biology: From Cryo-EM to Integrative Modelling was our final virtual conference of 2020, but there was no trace of Zoom fatigue amongst the 466 participants who joined us from 6 – 8 December!

80 international researchers presented their posters during the two posters sessions on the following topics:

  • Biophysical analysis in cells
  • COVID-19
  • Imaging across scales
  • Integrative modelling
  • Molecular sociology
  • Structural analysis in situ
  • Structural biology

Each of the participants had the chance to vote for their favourite poster, resulting in two posters winning the Best Poster Award kindly sponsored by EMBO Press.  Here are the winners:

New insights on the catalytic mechanism of arsenite oxidase

PHOTO: Filipa Engrola

Authors: Filipa Engrola, Márcia Correia, Teresa Santos-Silva, Maria Romao, (UCIBIO@FCT-NOVA, Portugal)

Arsenic (As) and antimony (Sb) are two metalloids that, due to anthropogenic and natural causes, pose an environmental  threat, considered as priority pollutants by the World Health Organisation and the United States Environmental Protection Agency. Although the safety guards recommend a maximum of 10 μg/L of As and Sb in drinking water, these values are exceeded in many regions worldwide, with no remediation approach that is simultaneously effective, clean and economically sustainable [1,2]. The ancient bioenergetic enzyme arsenite oxidase (Aio), from microorganisms Rhizobium sp. NT-26 (NT-26 Aio) and Alcaligenes faecalis (A.f. Aio), is currently being studied for its use as a biosensor and in bioremediation processes. Both Aio enzymes contain a large subunit (AioA) that harbours a molybdenum centre and a [3Fe-4S] cluster, and a small subunit (AioB) that possess a Rieske [2Fe-2S] cluster and have demonstrated to oxidise AsIII, as well as SbIII, into the easier to remove and less toxic forms of AsV and SbV, respectively [3,4]. Aiming to elucidate the catalysis mechanism of the enzymes, a combination of expression and purification of the proteins, crystallisation, structural analysis, enzyme kinetics and affinity tests were conducted. X-ray structures of the ligand-free form of the enzyme had been previously determined (PDB: 4AAY, 5NQD and 1G8K [3,5,6]). In our work, Aio crystals in complex with two different forms of the substrate analogue – Sb oxyanions, with a reaction kinetic 6500 times slower than AsIII [6] – diffracted up to ca 1.8 Å resolution. The structures show the reaction intermediates bound at the active site, with a μ-oxo bridge binding Sb to the Mo atom. Analysis of bond lengths and geometry of the ligands at the Mo active site allowed us to revisit the catalytic mechanism of As oxidation [7], contributing to the understanding and future biotechnological application of this family of enzymes in water treatment.

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Allosteric hotspot in the main protease of SARS-CoV-2

PHOTO: Léonie Ströhmich

Authors: Léonie Strömich, Sophia N Yaliraki, (Imperial College London, UK)

Since the beginning of 2020 we have seen the coronavirus SARS-CoV-2 causing a global pandemic with almost 34 million cases and over 1 million deaths worldwide [as of 01.10.2020] [1.] As a result, we have seen a surge in research efforts to develop effective treatments for the underlying disease, COVID-19. One approach is to target the main protease (Mpro) of SARS-CoV-2 as it is essential for virus replication in an early step of the viral life cycle [2.] Most efforts are centred on inhibiting the orthosteric binding site of the enzyme. However, considering allosteric sites on the protein allows for more selective drug design and widens the chemical search space. Here, we report an allosteric hotspot in the SARS-CoV-2 Mpro dimer by using novel atomistic graph theoretical methods: Markov transient analyses follow the propagation of a random walker on a graph and have been shown to successfully identify allosteric communication in catalytic proteins [3.] We further score the so identified allosteric hotspots against random sites in similar distances and thus identify a statistically significant putative allosteric site in the SARS-CoV-2 Mpro. We then simulate a binding event at this hotspot region using data from a recent XChem fragment screen by the Diamond Light Source [4.] which provides a starting point for rational drug design. This study uses highly efficient network theoretical models to shed light on allosteric communication and uncovers putative allosteric sites in the SARS-CoV-2 main protease. This provides a valuable contribution to the ongoing efforts to find a cure against COVID-19 by broadening the horizon for drug discovery efforts.

Image: Léonie Ströhmich

[1.] Official World Health Organization COVID-19
dashboard: (Accessed: 01.10.2020).
[2.] Hilgenfeld, R. (2014). FEBS Journal, 281(18), 4085-4096.
[3.] Amor, B., Yaliraki, S. N., Woscholski, R., & Barahona, M. (2014) Molecular BioSystems, 10(8), 2247-2258.
[4.] Douangamath, A., Fearon, D., Gehrtz, P., Krojer, T., Lukacik, P., Owen, C. D., … Walsh, M. A. (2020) Nature Communications, 11, 5047.

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Working on your own conference poster? Then check out these 8 tips for preparing a digital poster that stands out from the crowd.

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