Musings from the Tribbles Research and Innovation Network

This commentary integrates historical and modern findings that underpin our understanding of the cell-specific functions of the Tribbles (TRIB) proteins that bear on tumorigenesis. We touch on the initial discovery of roles played by mammalian TRIB proteins in a diverse range of cell-types and pathologies, for example, TRIB1 in regulatory T-cells, TRIB2 in acute myeloid leukaemia and TRIB3 in gliomas; the origins and diversity of TRIB1 transcripts; microRNA-mediated (miRNA) regulation of TRIB1 transcript decay and translation; the substantial conformational changes that ensue on binding of TRIB1 to the transcription factor C/EBPα; and the unique pocket formed by TRIB1 to sequester its C-terminal motif bearing a binding site for the E3 ubiquitin ligase COP1. Unashamedly, the narrative is relayed through the perspective of the Tribbles Research and Innovation Network, and its establishment, progress and future ambitions: the growth of TRIB and COP1 research to hasten discovery of their cell-specific contributions to health and obesity-related cancers.

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E3 Ubiquitin Ligase SPL2 Is a Lanthanide-Binding Protein

International Journal of Molecular Sciences ◽

10.3390/ijms22115712 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5712

Author(s):

Michał Tracz ◽

Ireneusz Górniak ◽

Andrzej Szczepaniak ◽

Wojciech Białek

Keyword(s):

Ubiquitin Ligase ◽

Conformational Changes ◽

Protein Interactions ◽

E3 Ubiquitin Ligase ◽

Lanthanide Ions ◽

E3 Ligases ◽

Fluorescence Measurements ◽

Partial Unfolding

The SPL2 protein is an E3 ubiquitin ligase of unknown function. It is one of only three types of E3 ligases found in the outer membrane of plant chloroplasts. In this study, we show that the cytosolic fragment of SPL2 binds lanthanide ions, as evidenced by fluorescence measurements and circular dichroism spectroscopy. We also report that SPL2 undergoes conformational changes upon binding of both Ca2+ and La3+, as evidenced by its partial unfolding. However, these structural rearrangements do not interfere with SPL2 enzymatic activity, as the protein retains its ability to auto-ubiquitinate in vitro. The possible applications of lanthanide-based probes to identify protein interactions in vivo are also discussed. Taken together, the results of this study reveal that the SPL2 protein contains a lanthanide-binding site, showing for the first time that at least some E3 ubiquitin ligases are also capable of binding lanthanide ions.

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RNF168-mediated localization of BARD1 recruits the BRCA1-PALB2 complex to DNA damage

Nature Communications ◽

10.1038/s41467-021-25346-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

John J. Krais ◽

Yifan Wang ◽

Pooja Patel ◽

Jayati Basu ◽

Andrea J. Bernhardy ◽

...

Keyword(s):

Dna Damage ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Coiled Coil ◽

Histone H2a ◽

Dna Breaks ◽

Diverse Range ◽

Dna Damage Signaling ◽

Dna Repair Proteins ◽

K 13

AbstractDNA damage prompts a diverse range of alterations to the chromatin landscape. The RNF168 E3 ubiquitin ligase catalyzes the mono-ubiquitination of histone H2A at lysine (K)13/15 (mUb-H2A), forming a binding module for DNA repair proteins. BRCA1 promotes homologous recombination (HR), in part, through its interaction with PALB2, and the formation of a larger BRCA1-PALB2-BRCA2-RAD51 (BRCA1-P) complex. The mechanism by which BRCA1-P is recruited to chromatin surrounding DNA breaks is unclear. In this study, we reveal that an RNF168-governed signaling pathway is responsible for localizing the BRCA1-P complex to DNA damage. Using mice harboring a Brca1CC (coiled coil) mutation that blocks the Brca1-Palb2 interaction, we uncovered an epistatic relationship between Rnf168− and Brca1CC alleles, which disrupted development, and reduced the efficiency of Palb2-Rad51 localization. Mechanistically, we show that RNF168-generated mUb-H2A recruits BARD1 through a BRCT domain ubiquitin-dependent recruitment motif (BUDR). Subsequently, BARD1-BRCA1 accumulate PALB2-RAD51 at DNA breaks via the CC domain-mediated BRCA1-PALB2 interaction. Together, these findings establish a series of molecular interactions that connect the DNA damage signaling and HR repair machinery.

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E6AP, an E3 ubiquitin ligase negatively regulates granulopoiesis by targeting transcription factor C/EBPα for ubiquitin-mediated proteasome degradation

Cell Death and Disease ◽

10.1038/cddis.2013.120 ◽

2013 ◽

Vol 4 (4) ◽

pp. e590-e590 ◽

Cited By ~ 17

Author(s):

P Pal ◽

S Lochab ◽

J K Kanaujiya ◽

I Kapoor ◽

S Sanyal ◽

...

Keyword(s):

Transcription Factor ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Proteasome Degradation ◽

Factor C

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RNF167 activates mTORC1 and promotes tumorigenesis by targeting CASTOR1 for ubiquitination and degradation

Nature Communications ◽

10.1038/s41467-021-21206-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Tingting Li ◽

Xian Wang ◽

Enguo Ju ◽

Suzane Ramos da Silva ◽

Luping Chen ◽

...

Keyword(s):

Breast Cancer ◽

Cell Proliferation ◽

Cancer Progression ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Cell Types ◽

Alternative Mechanism ◽

Central Controller ◽

Low Levels ◽

Mtorc1 Activation

AbstractmTORC1, a central controller of cell proliferation in response to growth factors and nutrients, is dysregulated in cancer. Whereas arginine activates mTORC1, it is overridden by high expression of cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1). Because cancer cells often encounter low levels of nutrients, an alternative mechanism might exist to regulate CASTOR1 expression. Here we show K29-linked polyubiquitination and degradation of CASTOR1 by E3 ubiquitin ligase RNF167. Furthermore, AKT phosphorylates CASTOR1 at S14, significantly increasing its binding to RNF167, and hence its ubiquitination and degradation, while simultaneously decreasing its affinity to MIOS, leading to mTORC1 activation. Therefore, AKT activates mTORC1 through both TSC2- and CASTOR1-dependent pathways. Several cell types with high CASTOR1 expression are insensitive to arginine regulation. Significantly, AKT and RNF167-mediated CASTOR1 degradation activates mTORC1 independent of arginine and promotes breast cancer progression. These results illustrate a mTORC1 regulating mechanism and identify RNF167 as a therapeutic target for mTORC1-dysregulated diseases.

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E3 Ubiquitin Ligase E6AP Negatively Regulates Adipogenesis by Downregulating Proadipogenic Factor C/EBPalpha

PLoS ONE ◽

10.1371/journal.pone.0065330 ◽

2013 ◽

Vol 8 (6) ◽

pp. e65330 ◽

Cited By ~ 15

Author(s):

Pooja Pal ◽

Savita Lochab ◽

Jitendra Kumar Kanaujiya ◽

Isha Kapoor ◽

Sabyasachi Sanyal ◽

...

Keyword(s):

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Factor C

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Unbiased identification of substrates for the Epac1-inducible E3 ubiquitin ligase component SOCS-3

Biochemical Society Transactions ◽

10.1042/bst20110629 ◽

2012 ◽

Vol 40 (1) ◽

pp. 215-218 ◽

Cited By ~ 11

Author(s):

Jamie J.L. Williams ◽

Timothy M. Palmer

Keyword(s):

Ubiquitin Ligase ◽

Protein Function ◽

E3 Ubiquitin Ligase ◽

Cell Types ◽

Specific Class ◽

Inhibitory Processes ◽

Receptor Signalling ◽

Ubiquitin Ligase Complex ◽

Multiple Cell ◽

Socs Protein

The anti-inflammatory effects of the prototypical second messenger cAMP have been extensively documented in multiple cell types. One mechanism by which these effects are achieved is via Epac1 (exchange protein directly activated by cAMP 1)-dependent induction of SOCS-3 (suppressor of cytokine signalling 3), which binds and inhibits specific class I cytokine receptors. One important aspect of SOCS-3 functionality is its role as the specificity determinant within an E3 ubiquitin ligase complex which targets cellular substrates for polyubiquitylation and proteasomal degradation. In the present review, we describe key inhibitory processes that serve to reduce cytokine receptor signalling, focusing primarily on SOCS protein function and regulation. We also outline a strategy we have developed to identify novel ubiquitylated substrates for the Epac1-inducible SOCS-3 E3 ubiquitin ligase complex following purification of the ubiquitinome. It is anticipated that identifying substrates for the Epac1-regulated SOCS-3 E3 ubiquitin ligase, and assessment of their functional significance, may pinpoint new sites for therapeutic intervention that would achieve therapeutic efficacy of cAMP-elevating drugs while minimizing the adverse effects usually associated with these agents.

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RNF168-mediated localization of BARD1 recruits the BRCA1-PALB2 complex to DNA damage

10.1101/2021.06.25.449923 ◽

2021 ◽

Author(s):

John J Krais ◽

Yifan Wang ◽

Pooja Patel ◽

Jayati Basu ◽

Andrea J Bernhardy ◽

...

Keyword(s):

Dna Damage ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Coiled Coil ◽

Histone H2a ◽

Dna Breaks ◽

Diverse Range ◽

Dna Damage Signaling ◽

Dna Repair Proteins ◽

K 13

DNA damage prompts a diverse range of alterations to the chromatin landscape. The RNF168 E3 ubiquitin ligase catalyzes the mono-ubiquitination of histone H2A at lysine (K)13/15 (mUb-H2A), forming a binding module for DNA repair proteins. BRCA1 promotes homologous recombination (HR), in part, through its interaction with PALB2, and the formation of a larger BRCA1-PALB2-BRCA2-RAD51 (BRCA1-P) complex. The mechanism by which BRCA1-P is recruited to chromatin surrounding DNA breaks is unclear. In this study, we reveal that an RNF168-governed signaling pathway is responsible for localizing the BRCA1-P complex to DNA damage. Using mice harboring a Brca1CC (coiled coil) mutation that blocks the Brca1-Palb2 interaction, we uncovered an epistatic relationship between Rnf168- and Brca1CC alleles, which disrupted development, and reduced the efficiency of Palb2-Rad51 localization. Mechanistically, we show that RNF168-generated mUb-H2A recruits BARD1 through a BRCT domain ubiquitin-dependent recruitment motif (BUDR). Subsequently, BARD1-BRCA1 accumulate PALB2-RAD51 at DNA breaks via the CC domain-mediated BRCA1-PALB2 interaction. Together, these findings establish a series of molecular interactions that connect the DNA damage signaling and HR repair machinery.

Download Full-text