A structural insight into the C-terminal RNA recognition motifs of T-cell intracellular antigen-1 protein

T-cell intracellular antigen-1 (TIA-1) plays a pleiotropic role in cell homeostasis through the regulation of alternative pre-mRNA splicing and mRNA translation by recognising uridine-rich sequences of RNAs. TIA-1 contains three RNA recognition motifs (RRMs) and a glutamine-rich domain. Here, we characterise its C-terminal RRM2 and RRM3 domains. Notably, RRM3 contains an extra novel N-terminal α-helix (α(1)) which protects its single tryptophan from the solvent exposure, even in the two-domain RRM23 context. The α(1) hardly affects the thermal stability of RRM3. On the contrary, RRM2 destabilises RRM3, indicating that both modules are tumbling together, which may influence the RNA binding activity of TIA-1.