TCEA2

TCEA2 is a testis-enriched transcription elongation factor of the TFIIS family that associates with the RNA polymerase II complex and contributes to maintaining genome stability during conflicts between transcription and replication (PMID:9441762, PMID:41062692). At sites of co-directional transcription-replication conflicts, the CUL3-KCTD10 E3 ubiquitin ligase ubiquitinates TCEA2 in a nonproteolytic manner, removing it from RNA polymerase II to transiently remodel the polymerase complex and permit replisome bypass; loss of KCTD10 causes TCEA2 retention, accumulation of transcription-replication conflicts, and elevated DNA damage (PMID:41062692, PMID:42128708). Consistent with this genome-protective role, TCEA2 physically and genetically interacts with BRCA1 in the response to transcription-associated DNA damage (PMID:25184681). At the transcriptional level, TCEA2 is induced downstream of the nuclear receptor FXR, which trans-activates response elements in the TCEA2 promoter in hepatocytes (PMID:23680185). Its testis-restricted expression pattern is distinct from the ubiquitously expressed TFIIS gene, indicating a specialized regulatory context (PMID:9441762).

1. 1997 Medium

   Established that TCEA2 is a distinct, testis-enriched member of the TFIIS transcription elongation factor family, separating it from the ubiquitous TFIIS gene and defining its tissue context.

   Evidence Genomic cloning, sequencing, and structural characterization of the TCEA2 gene

   PMID:9441762

   Open questions at the time

   • No direct biochemical demonstration of elongation activity for the TCEA2 protein itself
   • Functional consequence of testis-restricted expression not defined
   • No interaction partners identified at this stage
2. 2013 Medium

   Identified an upstream transcriptional regulator of TCEA2, showing it is induced by the nuclear receptor FXR through promoter response elements.

   Evidence Expression profiling and promoter trans-activation assays with FXR/RXR transfection and GW4064 activation in hepatocyte and hepatoma models

   PMID:23680185

   Open questions at the time

   • Functional consequence of FXR-driven TCEA2 induction not established
   • Single-lab study in liver-derived cells only
   • Connection between FXR regulation and TCEA2's genome-stability role unexplored
3. 2014 Medium

   Placed TCEA2 in the DNA damage response by identifying it as a BRCA1 physical and genetic interactor linked to transcription-associated damage.

   Evidence Systematic protein interaction screens for BRCA1 partners followed by genetic interaction analysis

   PMID:25184681

   Open questions at the time

   • Direct, reciprocally validated binding interface not mapped
   • Mechanism of how TCEA2 contributes to BRCA1 function unresolved
   • Single-lab screen-based identification
4. 2025 High

   Defined a mechanism by which TCEA2 is regulated at transcription-replication conflicts, showing CUL3-KCTD10 nonproteolytically ubiquitinates TCEA2 to remodel RNA polymerase II and permit replisome bypass.

   Evidence Co-IP/interaction studies, ubiquitination assays, and KCTD10 knockout cells with TRC and DNA damage readouts

   PMID:41062692

   Open questions at the time

   • Ubiquitination site(s) on TCEA2 and how they trigger removal not detailed
   • Structural basis of RNA Pol II remodeling unresolved
   • Whether the BRCA1 and FXR axes intersect with the KCTD10 pathway untested
5. 2026 Medium

   Clarified that the KCTD10-mediated modification is nonproteolytic and serves as a remodeling rather than a degradation signal for TCEA2.

   Evidence Mechanistic review synthesizing the KCTD10-TCEA2 ubiquitination data

   PMID:42128708

   Open questions at the time

   • Review corroborating a single primary study; no new independent experimental data
   • Reader machinery interpreting the nonproteolytic ubiquitin mark not identified

• How TCEA2's testis-enriched expression, FXR transcriptional control, and BRCA1 interaction integrate with its KCTD10-regulated role at transcription-replication conflicts remains unresolved.
• No unified model linking the regulatory inputs (FXR), partners (BRCA1), and the KCTD10 ubiquitination mechanism
• Physiological role in testis tissue uncharacterized