GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE322nnn/GSE322555/primaryOK200OtherHomo sapiensOtherhttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE322555GEOGSEfalseCRISPR-Cas9 Screening Identifies UBE3C as a Top Negative Regulator of THEMIS Protein ExpressionTHEMIS is an essential T-cell receptor signal modulator critical for T-cell development and peripheral homeostasis; however, the machinery governing its protein stability remains elusive. Utilizing unbiased CRISPR/Cas9 screening integrated with affinity purification-mass spectrometry, we identify UBE3C as the physiological E3 ligase for THEMIS. Mechanistically, UBE3C interacts with the CABIT1 domain of THEMIS and catalyzes K48-linked polyubiquitination, primarily targeting the conserved Lysine 208 residue for proteasomal degradation. UBE3C deletion in T cells in vivo results in normal thymic T cell development but causes an age-dependent defect in peripheral T cell homeostasis. Most critically, genetic epistasis analysis demonstrates that UBE3C deletion alleviates the developmental block in Themis+/- mice and rescues the peripheral homeostatic defects of UBE3C-deficient mice. Our findings establish the UBE3C-THEMIS axis as the core ubiquitin-dependent protein quality control module, revealing an unrecognized role for UBE3C in adaptive immunity and providing a molecular explanation for the exquisite dosage sensitivity of THEMIS.2026/04/30GSE322555GSM9554213GSM9554214GSM9554215GSM9554216GSM9554217GSM955421821697322555Homo sapiens