TACC1

TACC1 is a centrosomal/cytoskeletal scaffold protein that couples microtubule dynamics to cell division and also functions in transcriptional regulation (PMID:15064709, PMID:26012630). Through its conserved C-terminal TACC domain, TACC1 acts as a microtubule plus-end tracking protein that maintains normal microtubule growth speed, with partial functional redundancy with TACC3 (PMID:26012630). During mitosis TACC1 assembles into complexes with the microtubule-associated protein chTOG and the adaptor TRAP, and partitions between Aurora kinase pools: it works with Aurora A and chTOG to support cell division, and forms a complex with Aurora B that drives its localization to the midbody during cytokinesis — Aurora B depletion mislocalizes TACC1 and produces multinucleated cells, placing Aurora B upstream of TACC1 (PMID:14603251, PMID:15064709). TACC1 cycles to the nucleolus in interphase and into the chromatin-enriched nuclear fraction, where it serves as a nuclear receptor coregulator: it binds unliganded thyroid hormone and retinoic acid receptors and is required for their ligand-dependent transcriptional activity and proper nuclear retention (PMID:15064709, PMID:20078863). TACC1 additionally associates with the Sm-like RNA-processing proteins LSM7 and SmG, linking it to mRNA regulation (PMID:12165861, PMID:14603251). Inappropriate TACC1 overexpression transforms fibroblasts and confers anchorage-independent growth (PMID:10435627).

1. 1999 Medium

   Established that TACC1 dysregulation has oncogenic potential, motivating investigation of its normal cellular function.

   Evidence CMV-driven overexpression in mouse fibroblasts with anchorage-independent growth assay

   PMID:10435627

   Open questions at the time

   • No molecular mechanism linking TACC1 to proliferation defined
   • No endogenous loss-of-function data
2. 2002 Medium

   Identified TACC1's first physical partners, placing it in both an mRNA-processing context (LSM7, SmG) and a microtubule context (chTOG), and a transcription-factor context (GAS41), revealing its multi-complex scaffold nature.

   Evidence Yeast two-hybrid screens, GST pulldown, co-immunoprecipitation and domain mapping; immunolocalization to perinuclear cytoplasm

   PMID:11903063 PMID:12165861

   Open questions at the time

   • Functional consequence of LSM7/SmG binding for mRNA processing not tested
   • chTOG and GAS41 interactions not yet linked to a cellular phenotype
3. 2003 Medium

   Connected TACC1 to mitotic machinery by showing it forms a chTOG/TRAP/Aurora A/LSM7 complex and that its depletion perturbs cell division.

   Evidence Co-immunoprecipitation and siRNA knockdown with cell-division phenotype readout

   PMID:14603251

   Open questions at the time

   • TACC1 knockdown effect weaker than chTOG, leaving its individual contribution unclear
   • Order of assembly within the complex not resolved
4. 2004 High

   Defined TACC1's cell-cycle-dependent localization and placed Aurora B upstream of its midbody recruitment during cytokinesis.

   Evidence Immunofluorescence, reciprocal co-IP, and Aurora B RNAi with multinucleation readout

   PMID:15064709

   Open questions at the time

   • Direct phosphorylation of TACC1 by Aurora B not demonstrated
   • Mechanism of nucleolar relocalization in interphase unknown
5. 2010 High

   Established a nuclear function for TACC1 as a coregulator that scaffolds unliganded thyroid and retinoic acid receptors and supports their transcriptional output and nuclear retention.

   Evidence Yeast two-hybrid, GST pulldown, co-IP, subcellular fractionation, and siRNA with transcriptional reporter assays

   PMID:20078863

   Open questions at the time

   • Identity of co-recruited transcriptional machinery not defined
   • How TACC1 switches between cytoplasmic/mitotic and nuclear roles is unknown
6. 2015 Medium

   Demonstrated a direct cytoskeletal activity: TACC1 is a microtubule plus-end tracking protein whose TACC domain confers plus-end localization and regulates microtubule growth.

   Evidence Live imaging of GFP-TACC1 in Xenopus embryonic cells, domain-deletion mutants, and morpholino knockdown with microtubule dynamics tracking

   PMID:26012630

   Open questions at the time

   • Mechanism of plus-end recognition by the TACC domain not resolved
   • Relationship between +TIP activity and mitotic complex function not integrated
7. 2021 Low

   Linked a TACC1 splice variant to suppression of proliferation and induction of autophagy via the AKT/mTOR axis.

   Evidence Overexpression of TACC1v25 in HNSCC cell lines, Western blotting, and pharmacological rescue with the AKT activator SC79

   PMID:34897285

   Open questions at the time

   • Pathway placement inferred from pharmacological rescue without direct binding partner
   • Single cell-line context; isoform-specific generality untested
8. 2026 Low

   Proposed a TACC1-PARP1 interaction and an upstream LEF1/NFE2L3 transcriptional axis activating AKT/mTOR and inhibiting apoptosis.

   Evidence Co-IP/mass spectrometry, ChIP-seq, Western blotting, functional assays, and xenograft model

   PMID:42182760

   Open questions at the time

   • Direct interaction not validated by reciprocal or reconstitution assays
   • Pathway placement based on correlative expression changes without mutagenesis

• How TACC1 partitions between its mitotic microtubule/Aurora roles, its nuclear receptor coregulator role, and its mRNA-processing associations — and what regulates these transitions — remains unresolved.
• No structural model of the TACC domain bound to microtubule plus-ends or to nuclear receptors
• Whether the mRNA-processing, mitotic, and transcriptional functions reflect distinct isoforms or a single regulated protein is unknown