Falcon (Edison Scientific Literature) deep research report on human TIA1 (UniProt P31483)
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TIA1 is a multifunctional RNA-binding protein that couples RNA recognition via folded
RRMs to biomolecular condensation/phase separation via low-complexity regions, switching
between nuclear RNA processing and cytoplasmic stress responses.
"A central conceptual framework in the recent literature is that TIA1 couples **RNA recognition (via folded RRMs)** to **biomolecular condensation/phase separation (via low-complexity regions)**, enabling condition-dependent switching between nuclear RNA processing and cytoplasmic stress responses."
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RRM2 is the dominant high-affinity sequence-specific RNA-binding domain, RRM3
enhances/cooperates with RRM2, and RRM1 contributes little intrinsic RNA-binding affinity.
"- **RRM2** is the dominant high-affinity, sequence-specific RNA-binding domain.
- **RRM3** enhances/cooperates with RRM2.
- **RRM1** has little intrinsic RNA-binding affinity and contributes minimally to binding in several contexts, although it can modulate selectivity/architecture in some assays."
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TIA1 preferentially binds uridine-rich/pyrimidine-rich RNA, including 3' U-rich elements
and intronic U-rich motifs commonly 10-28 nucleotides downstream of 5' splice sites.
"A transcriptome-wide iCLIP study and structural studies converge on the positional rule that TIA binding is commonly **~10–28 nucleotides downstream of exon–intron boundaries/5′ splice sites**, consistent with a role in 5′ splice-site definition."
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TIA1 enhances recognition of weak 5' splice sites by binding downstream U-rich sequences
and assisting U1 snRNP recruitment via the U1-C protein, exemplified by FAS exon 6.
"A well-established mechanistic function of TIA1 is **enhancing recognition of weak 5′ splice sites** through binding to downstream U-rich sequences and recruitment/assistance of **U1 snRNP**, specifically via the **U1-C** protein."
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The C-terminal low-complexity/prion-like domain drives liquid-liquid phase separation
and stress granule assembly, linking eIF2-alpha-dependent translational arrest to
cytoplasmic mRNA triage.
"The **C-terminal low-complexity/prion-like domain** is a major determinant of condensation/LLPS and SG assembly."
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Structural/biophysical work shows TIA1 RRM2-RRM3 binds poly-uridine and FAS-derived
pyrimidine-rich RNA with nanomolar affinity, with RNA binding inducing a compact
cooperative RRM arrangement.
"Structural/biophysical work reports that **TIA1 RRM2–RRM3 binds poly-uridine and FAS-derived pyrimidine-rich RNA with nanomolar affinity**, and that RNA binding drives a more compact RRM arrangement (consistent with cooperative avidity)."
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In germinal center B cells, TIA1/TIAL1 directly bind Mcl1 mRNA and promote MCL1 protein
expression, protecting cells from apoptosis and enabling high-affinity antibody responses.
"Mechanistically, TIA1/TIAL1 directly bind **Mcl1 mRNA** and promote **MCL1 protein expression**, protecting GC B cells from apoptosis and enabling productive, high-affinity antibody responses."
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Disease-linked mutations in the low-complexity domain (e.g., Welander distal myopathy
p.E384K and ALS/FTD variants) can delay stress granule disassembly or perturb phase
behavior, shifting reversible assemblies toward persistent/aberrant states.
"Disease-linked mutations in this domain are proposed to alter phase behavior and SG dynamics, potentially shifting reversible SG assemblies toward more persistent/aberrant states."