Characterization of Novel Substrates of the Tankyrase and RNF146 Destruction Complex and Mechanisms of its Regulation
Bibliographic record
Abstract
Poly-ADP-ribose is a post-translational modification that was first described over 50 years ago as a polymer derived from nicotinamide adenine dinucleotide or NAD. Since then, a family of 17 enzymes responsible for generating Poly-ADP-ribosylation or PARylation post translational modification has been identified and characterized. A unique member of this family of enzymes, called Poly-ADP-ribose Polymerases (PARPs), are Tankyrases. There are two mammalian Tankyrases, Tankyrase 1 and 2, whose domain organization include ankyrin repeat clusters which mediate enzyme-substrate interactions and a SAM domain which regulates oligomerization of Tankyrase into large macromolecular complexes. Tankyrases bind to proteins through a ‘RxxxxG’ peptide motif which facilities these proteins to undergo PARylation. A subset of Tankyrase substrates are recognized by an E3 ligase, RNF146, which facilities protein degradation through PARylation dependent ubiquitylation. The studies summarized in this thesis have focused on the identification of new proteins targets involved in the Tankyrase:RNF146 degradation pathway and investigates how Tankyrase PARylation is regulated through FIH dependent hydroxylation. I have identified SH3BP5 and SH3BP5L as new Tankyrase substrates that are targets of RNF146. I have shown that both substrates are guanine exchange factors for the small GTPase Rab11a. I have defined the minimal catalytic core of SH3BP5/L and shown it to be composed of a novel two α-helix GEF domain. My work has demonstrated that SH3BP5 and SH3BP5L are both required for optimal activation of Rab11a in epithelial cells during lumenogenesis and that their activities are repressed by Tankyrase-mediated PARylation. RNF146 regulates Rab11a activity by controlling Tankyrase protein abundance, marking the first time that RNF146 has been described as antagonistic towards Tankyrase function. I have demonstrated that FIH-mediated hydroxylation of Tankyrase affects the ability of substrates to bind to the ankyrin repeat clusters and inhibits autoPARylation and substrate PARylation yet does not affect protein degradation. Since PARylation dependant degradation is unaffected, it suggests that hydroxylation could affect the degradation independent functions of Tankyrase.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".