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3 results on '"Bertsoulaki E"'

1. Characterisation of USP31, the 3rd microtubule localising Deubiquitylase

Author

Bertsoulaki, E., Clague, Michael, Urbe, Sylvie, and Pizer, Barry

Subjects
572
Abstract

Ubiquitylation is a reversible modification with a variety of roles ranging from governing protein homeostasis and trafficking to DNA damage and the immune response. A ubiquitin molecule is added on a substrate protein by an orchestrated cascade of reactions performed by the E1, E2 and E3 enzymes, while it is removed by the Deubiquitylases (DUBs). This work reports for the first time on a hitherto uncharacterised DUB enzyme, USP31. I identified USP31 in a screen for regulation of the MYCN oncogene in neuroblastoma. However, my initial characterisation showed that USP31 localises on microtubules and the centrosome. I proceeded to map the microtubule localising sequence of USP31 to the unstructured C-terminal of the protein. From that point, I developed a variety of cellular models in order to study its effect on microtubule network properties and the downstream processes they govern.

Published
2018
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2. The centrosomal deubiquitylase USP21 regulates Gli1 transcriptional activity and stability

Author

Heride C, Dj, Rigden, Bertsoulaki E, Cucchi D, De Smaele E, Mj, Clague, and Sylvie Urbe

Subjects
Transcriptional Activation, Gli1, DUB, Zinc Finger Protein GLI1, Gene Knockout Techniques, Mice, Two-Hybrid System Techniques, Animals, Humans, Hedgehog Proteins, Protein Interaction Domains and Motifs, PKA, Phosphorylation, Adaptor Proteins, Signal Transducing, Gene Library, Centrosome, Protein Stability, Ubiquitin, Cullin Proteins, Ubiquitin Hedgehog Gli1 PKA Phosphorylation DUB, NIH 3T3 Cells, Ubiquitin Thiolesterase, Hedgehog, Protein Binding, Signal Transduction, Research Article
Abstract

USP21 is a centrosome-associated deubiquitylase (DUB) that has been implicated in the formation of primary cilia – crucial organelles for the regulation of the Hedgehog (Hh) signaling pathway in vertebrates. Here, we identify KCTD6 – a cullin-3 E3-ligase substrate adapter that has been previously linked to Hh signaling – as well as Gli1, the key transcription factor responsible for Hh signal amplification, as new interacting partners of USP21. We identify a cryptic structured protein interaction domain in KCTD6, which is predicted to have a similar fold to Smr domains. Importantly, we show that both depletion and overexpression of catalytically active USP21 suppress Gli1-dependent transcription. Gli proteins are negatively regulated through protein kinase A (PKA)-dependent phosphorylation. We provide evidence that USP21 recruits and stabilises Gli1 at the centrosome where it promotes its phosphorylation by PKA. By revealing an intriguing functional pairing between a spatially restricted deubiquitylase and a kinase, our study highlights the centrosome as an important hub for signal coordination., Summary: We identify a Hedgehog-pathway-associated ubiquitin ligase adapter as a direct interaction partner of the deubiquitylase USP21 and discover a close interplay between USP21 and protein kinase A in regulating Gli1.

Published
2016

3. A Chlamydia effector combining deubiquitination and acetylation activities induces Golgi fragmentation.

Author

Pruneda JN, Bastidas RJ, Bertsoulaki E, Swatek KN, Santhanam B, Clague MJ, Valdivia RH, Urbé S, and Komander D

Subjects
A549 Cells, Acetylation, Acetyltransferases chemistry, Animals, Bacterial Proteins genetics, Bacterial Proteins metabolism, Chlamydia trachomatis genetics, Chlorocebus aethiops, Deubiquitinating Enzymes genetics, Gene Expression Regulation, Bacterial, Golgi Apparatus ultrastructure, HeLa Cells, Humans, Models, Molecular, Mutation, Protein Conformation, Vero Cells, Acetyltransferases genetics, Chlamydia Infections metabolism, Chlamydia trachomatis metabolism, Deubiquitinating Enzymes chemistry, Golgi Apparatus metabolism, Protein Processing, Post-Translational
Abstract

Pathogenic bacteria are armed with potent effector proteins that subvert host signalling processes during infection 1 . The activities of bacterial effectors and their associated roles within the host cell are often poorly understood, particularly for Chlamydia trachomatis 2 , a World Health Organization designated neglected disease pathogen. We identify and explain remarkable dual Lys63-deubiquitinase (DUB) and Lys-acetyltransferase activities in the Chlamydia effector ChlaDUB1. Crystal structures capturing intermediate stages of each reaction reveal how the same catalytic centre of ChlaDUB1 can facilitate such distinct processes, and enable the generation of mutations that uncouple the two activities. Targeted Chlamydia mutant strains allow us to link the DUB activity of ChlaDUB1 and the related, dedicated DUB ChlaDUB2 to fragmentation of the host Golgi apparatus, a key process in Chlamydia infection for which effectors have remained elusive. Our work illustrates the incredible versatility of bacterial effector proteins, and provides important insights towards understanding Chlamydia pathogenesis.

Published
2018
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