Structural mechanism of BRD4-NUT and p300 bipartite interaction in propagating aberrant gene transcription in chromatin in NUT carcinoma.

BRD4-NUT, a driver fusion mutant in rare and highly aggressive NUT carcinoma, acts in aberrant transcription of anti-differentiation genes by recruiting histone acetyltransferase (HAT) p300 and promoting p300-driven histone hyperacetylation and nuclear condensation in chromatin. However, the molecular basis of how BRD4-NUT recruits and activates p300 remains elusive. Here, we report that BRD4-NUT contains two transactivation domains (TADs) in NUT that bind to the TAZ2 domain in p300. Our NMR structures reveal that NUT TADs adopt amphipathic helices when bound to the four-helical bundle TAZ2 domain. The NUT protein forms liquid-like droplets in-vitro that are enhanced by TAZ2 binding in 1:2 stoichiometry. The TAD/TAZ2 bipartite binding in BRD4-NUT/p300 triggers allosteric activation of p300 and acetylation-driven liquid-like condensation on chromatin that comprise histone H3 lysine 27 and 18 acetylation and transcription proteins BRD4L/S, CDK9, MED1, and RNA polymerase II. The BRD4-NUT/p300 chromatin condensation is key for activating transcription of pro-proliferation genes such as ALX1, resulting ALX1/Snail signaling and epithelial-to-mesenchymal transition. Our study provides a previously underappreciated structural mechanism illuminating BRD4-NUT's bipartite p300 recruitment and activation in NUT carcinoma that nucleates a feed-forward loop for propagating histone hyperacetylation and chromatin condensation to sustain aberrant anti-differentiation gene transcription and perpetual tumor cell growth.

Outcomes of STN-DBS in PD Patients With Different Rates of Disease Progression Over One Year of Follow-Up.

Parkinson's disease (PD) is a progressive neurodegenerative disorder, and the rate of progression is different across individuals. Subthalamic nucleus deep brain stimulation (STN-DBS) has been shown to produce long-term symptom improvement in PD. In this retrospective study, we wanted to explore the effects of bilateral STN-DBS in PD patients with different rates of disease progression. Forty patients with PD were included. An index of progression rate was calculated by the ratio of the Unified Parkinson Disease Rating Scale, part III (UPDRS-III), score in the off-medication condition at baseline and disease duration. The patients were divided into fast-, medium-, and slow-progression groups by this index. The outcome measurements at the 1st, 6th, and 12th months after surgery were the changes in UPDRS-III scores in the off-medication/on-stimulation condition compared with the baseline. We found the following. (1). Motor functions in the different PD progression groups were improved by bilateral STN-DBS treatment at 1 year of follow-up. (2). However, compared to the slow- and medium-progression groups, the fast-progression group had less improvement at the 6th- and 12th-month follow-up. The results indicated that bilateral STN-DBS can improve motor functions of Parkinson's patients over the 1-year follow-up. Moreover, the outcomes in the slow- and medium-progression patients were better than those with fast-progression rates.

Roles of the BRD4 short isoform in phase separation and active gene transcription.

BRD4, a major tandem-bromodomain-containing transcription regulator, has two isoforms. The long isoform (BRD4L) has an extended C terminus that binds transcription cofactors, while the short isoform (BRD4S) lacks this C-terminal extension. Unlike BRD4L, the role of BRD4S in gene transcription remains unclear. Here, we report that, in human cancer cells, BRD4S forms nuclear puncta that possess liquid-like properties and that colocalize with BRD4L, MED1 and sites of histone H3 lysine 27 acetylation. BRD4 puncta are correlated with BRD4S but not BRD4L expression levels. BRD4S knockdown reduces BRD4S condensation, and ectopic expression promotes puncta formation and target gene transcription. BRD4S nuclear condensation is mediated by its intrinsically disordered regions and binding of its bromodomains to DNA and acetylated chromatin, respectively, and BRD4S phosphorylation diminishes BRD4 condensation. Our study illuminates a previously unappreciated role of BRD4S in organizing chromatin and transcription factors through phase separation to sustain gene transcription in chromatin for cancer cell proliferation.