TXNL4B (thioredoxin like 4B) is an essential spliceosomal protein that plays critical roles in pre-mRNA splicing and cell cycle regulation. Structurally, TXNL4B adopts a thioredoxin fold and functions as part of the U4/U6·U5 tri-snRNP complex, where it specifically associates with the minor spliceosome along with CENATAC 1. The protein interacts with Prp6, an integral component of the tri-snRNP complex, through its N-terminal region (residues 1-33), though this region extends into the β-sheet core of its thioredoxin-fold structure 2. TXNL4B demonstrates regulatory functions beyond splicing, as it influences bioavailable testosterone levels by reducing sex hormone-binding globulin (SHBG) 3. The gene shows clinical relevance through genetic associations with multiple diseases: variants at 16q22.2 containing TXNL4B are associated with IgA nephropathy susceptibility in Han Chinese populations 4, and 16q deletions encompassing TXNL4B correlate with improved survival in breast cancer patients, particularly in Luminal A subtypes 5. Additionally, TXNL4B expression is modulated by anti-inflammatory compounds and may contribute to inflammatory responses 6. The protein's high-resolution crystal structure has been determined at 1.33 Å resolution, revealing detailed molecular architecture important for its spliceosomal functions 2.