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The Ku heterodimer, composed of subunits Ku70 and Ku80, is known for its essential role in repairing double-stranded DNA breaks via non-homologous end joining (NHEJ). We previously identified Ku70 S155 as a novel phosphorylation site within the von Willebrand A-like (vWA) domain of Ku70 and documented an altered DNA damage response in cells expressing a Ku70 S155D phosphomimetic mutant. Here, we conducted proximity-dependent biotin identification (BioID2) screening using wild-type Ku70, Ku70 S155D mutant, and Ku70 with a phosphoablative substitution (S155A) to identify Ku70 S155D-specific candidate proteins that may rely on this phosphorylation event. Using the BioID2 screen with multiple filtering approaches, we compared the protein interactor candidate lists for Ku70 S155D and S155A. TRIP12 was exclusive to the Ku70 S155D list, considered a high confidence interactor based on SAINTexpress analysis, and appeared in all three biological replicates of the Ku70 S155D-BioID2 mass spectrometry results. Using proximity ligation assays (PLA), we demonstrated a significantly increased association between Ku70 S155D-HA and TRIP12 compared to wild-type Ku70-HA cells. In addition, we were able to demonstrate a robust PLA signal between endogenous Ku70 and TRIP12 in the presence of double-stranded DNA breaks. Finally, co-immunoprecipitation analyses showed an enhanced interaction between TRIP12 and Ku70 upon treatment with ionizing radiation, suggesting a direct or indirect association in response to DNA damage. Altogether, these results suggest an association between Ku70 phospho-S155 and TRIP12. [ABSTRACT FROM AUTHOR]

Clark–Baraitser syndrome is a rare autosomal dominant intellectual disability syndrome caused by pathogenic variants in the TRIP12 (Thyroid Hormone Receptor Interactor 12) gene. TRIP12 encodes an E3 ligase in the ubiquitin pathway. The ubiquitin pathway includes activating E1, conjugating E2 and ligating E3 enzymes which regulate the breakdown and sorting of proteins. This enzymatic pathway is crucial for physiological processes. A significant proportion of TRIP12 variants are currently classified as variants of unknown significance (VUS). Episignatures have been shown to represent a powerful diagnostic tool to resolve inconclusive genetic findings for Mendelian disorders and to re-classify VUSs. Here, we show the results of DNA methylation episignature analysis in 32 individuals with pathogenic, likely pathogenic and VUS variants in TRIP12. We identified a specific and sensitive DNA methylation (DNAm) episignature associated with pathogenic TRIP12 variants, establishing its utility as a clinical biomarker for Clark–Baraitser syndrome. In addition, we performed analysis of differentially methylated regions as well as functional correlation of the TRIP12 genome-wide methylation profile with the profiles of 56 additional neurodevelopmental disorders. [ABSTRACT FROM AUTHOR]

The Thyroid hormone Receptor Interacting Protein 12 (TRIP12) protein belongs to the 28-member Homologous to the E6-AP C-Terminus (HECT) E3 ubiquitin ligase family. First described as an interactor of the thyroid hormone receptor, TRIP12's biological importance was revealed by the embryonic lethality of a murine model bearing an inactivating mutation in the TRIP12 gene. Further studies showed the participation of TRIP12 in the regulation of major biological processes such as cell cycle progression, DNA damage repair, chromatin remodeling, and cell differentiation by an ubiquitination-mediated degradation of key protein substrates. Moreover, alterations of TRIP12 expression have been reported in cancers that can serve as predictive markers of therapeutic response. The TRIP12 gene is also referenced as a causative gene associated to intellectual disorders such as Clark–Baraitser syndrome and is clearly implicated in Autism Spectrum Disorder. The aim of the review is to provide an exhaustive and integrated overview of the different aspects of TRIP12 ranging from its regulation, molecular functions and physio-pathological implications. [ABSTRACT FROM AUTHOR]