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During the congress, E-Posters will be accessible to all participants on the congress website 24/7, as well as in the E-poster stations in the congress center.
Preparing your E-Poster
Please review the E-Poster format requirements carefully when preparing your E-Poster. Should your E-Poster not meet the mentioned requirements, it may not be displayed as described above.
E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
Please follow the instructions below to input your abstract title.
Abstract titles should be brief and reflect the content of the abstract.
Vasopressin stimulates Aqp2 gene transcription in kidney collecting duct cells, increasing water reabsorption. We previously demonstrated that β-Catenin (CTNNB1) and PARP1 are implicated in vasopressin-responsive Aqp2 transcription, but the underlying the transcriptional regulatory mechanisms remain unclear. In this study, we introduce a bromodomain protein, Tripartite motif-containing 28 (TRIM28, also known as KAP1), interacting with the CTNNB1-PARP1 into the transcriptional machinery that controls RNA polymerase II (Pol II) transcription pausing and release in Aqp2 regulation.
Experiments were performed in the mouse collecting duct cell line (mpkCCD), grown on semipermeable filters and treated with dDAVP (1 nM) for 24 h to induce AQP2 expression. siRNA-mediated knockdown of Ctnnb1 or Trim28 was performed using a reverse transfection strategy. To identify key transcriptional regulators, we combined RNA sequencing (RNA-Seq)-based transcriptomics, bioinformatics, co-immunoprecipitation (co-IP), and Pol II chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR).
Transcriptomic and bioinformatic analyses identified transcriptional regulators potentially involved in the functional association between vasopressin signaling and CTNNB1-dependent mechanisms in the regulation of Aqp2 transcription. Among the top 20 transcriptional regulators identified from each pathway, several were associated with Pol II activity, including factors involved in Pol II initiation (Tbp, Gtf2b, Gtf2e2) and elongation (Cdk9, Brd4, Ell2, Supt6, Ctr9, Nelfe, Nelfa). Guided by prior evidence that PARP1 interacts with CTNNB1 in Aqp2 regulation and that CDK9 and BRD4 modulate Pol II elongation, we assembled a protein–protein interaction network and computed the intersection of the CTNNB1, PARP1, CDK9, and BRD4 interactomes from the Protein Interaction Database (BioGRID). Among these, TRIM28 (KAP1) emerged as a key bromodomain-containing protein involved in Pol II activity. Co-IP experiments showed that TRIM28 physically associates with Pol II, CDK9, CTNNB1, and PARP1, forming a transcriptional complex at the Aqp2 promoter that governs Pol II promoter-proximal pausing and pause release. Consistently, siRNA-mediated Trim28 knockdown significantly attenuated dDAVP-induced Aqp2 mRNA and protein abundance. ChIP-qPCR demonstrated that Trim28 knockdown markedly reduced Pol II occupancy at the Aqp2 promoter in response to dDAVP stimulation. Furthermore, immunofluorescence staining revealed that TRIM28 formed dynamic nuclear condensates whose number per nucleus increased upon dDAVP treatment, suggesting phase separation-mediated transcriptional regulation.
These findings establish TRIM28 as a critical component of a transcriptional scaffold that modulates Pol II recruitment, stabilization, and elongation at the Aqp2 gene, thereby enhancing vasopressin-responsive water reabsorption in the kidney collecting duct.
