The Inhibitor of Apoptosis (IAP) Ubiquitome

Abstract

The Inhibitor of Apoptosis (IAP) proteins are a highly conserved group of anti-apoptotic proteins. Cellular IAP 1 and 2 (cIAP1 and 2) are two members of the IAP protein family that regulate the activity of the Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor family. The role and mechanism of the IAPs in ubiquitination are not yet completely understood due to the complexity of this posttranslational modification process. Additionally, The IAPs are involved in a myriad of cellular processes, and many of the process-specific mechanisms by which the IAPs are involved is unknown. I aim to delve deeper into the signalling pathways that are controlled by cIAP1 and cIAP2 by discovering currently unknown protein-protein interactions. In doing so, I will determine which proteins interact with the cIAPs and what signalling pathways these proteins are involved in. Using a BioID approach, I sought to characterize the cIAP1 interactors involved in the canonical and non-canonical NF-κB pathways. I generated a stable cell line expressing TurboID-cIAP1 fusion protein in HEK 293T cells that expressTurboID-cIAP1 at levels comparable to endogenous cIAP1. I identified multiple potential cIAP1 interactors that have ties to the NF-κB pathway. These proteins regulate NF-κB signalling in multiple ways including influencing acetylation and nuclear retention of the NF-κB transcription factors, phosphorylation of NF-κB transcription factors, and RNA splicing of genes involved in the TNFR1 complex I. Further work needs to be done to confirm these interactions and to discover the mechanisms by which these interactions occur. NF-κB signalling is known to have widespread function within the cell and within diseases such as cancer; it will be beneficial to study these interactions to better understand how cancer develops and how to treat it best, especially in patients with a poor prognosis.