Project description:The addressable pocket of a target protein is often not functionally relevant. This is particularly true for multidomain gene regulatory proteins, such as the bromodomain-containing transcriptional regulator TRIM24. TRIM24 has been posited as a dependency in numerous human cancers, yet potent and selective ligands for the TRIM24 bromodomain do not exert effective anti-proliferative responses. We therefore repositioned these probes as targeting features for heterobifunctional protein degraders.
Project description:The addressable pocket of a target protein is often not functionally relevant. This is particularly true for multidomain gene regulatory proteins, such as the bromodomain-containing transcriptional regulator TRIM24. TRIM24 has been posited as a dependency in numerous human cancers, yet potent and selective ligands for the TRIM24 bromodomain do not exert effective anti-proliferative responses. We therefore repositioned these probes as targeting features for heterobifunctional protein degraders.
Project description:The addressable pocket of a target protein is often not functionally relevant. This is particularly true for multidomain gene regulatory proteins, such as the bromodomain-containing transcriptional regulator TRIM24. TRIM24 has been posited as a dependency in numerous human cancers, yet potent and selective ligands for the TRIM24 bromodomain do not exert effective anti-proliferative responses. We therefore repositioned these probes as targeting features for heterobifunctional protein degraders.
Project description:Heterobifunctional proteolysis-targeting chimeric compounds leverage the activity of E3 ligases to induce degradation of target oncoproteins and exhibit potent preclinical antitumor activity. To dissect the mechanisms regulating tumor cell sensitivity to different classes of pharmacological "degraders" of oncoproteins, we performed genome-scale CRISPR/Cas9-based gene-editing studies. We observed that myeloma cell resistance to "degraders" of different targets (BET bromodomain proteins, CDK9) and operating through CRBN (degronimids) or VHL is primarily mediated by prevention of, rather than adaptation to, breakdown of the target oncoprotein; involves loss-of-function for the cognate E3 ligase or interactors/regulators of the respective cullin-RING ligase (CRL) complex. The substantial gene-level differences for CRBN- vs. VHL-based degraders explains mechanistically the lack of cross-resistance for degraders targeting the same protein via different E3 ligase/CRLs.
Project description:Cancer arises from the malignant interplay between oncogenic signaling and cell specification. Transcriptionally activated stem, growth and survival programs reshape an epigenomic identity defined by a transcriptional core regulatory circuitry. To study and disrupt oncogenic transcription, we first created inhibitors of BET bromodomains. Selective antagonism of oncogenic transcriptional signaling arises from bromodomain-specific activity. Recently, we innovated a strategy to induce selective and pronounced degradation of BET coactivator proteins via phthalimide conjugation for E3 ubiquitin ligase recruitment. Degraders of BET bromdomains (dBETs) exhibited superior efficacy to bromodomain inhibitors in cultivated leukemia cells, through unknown mechanisms. Here, we use chemically optimized small-molecule degronimids and kinetic measures of chromatin structure and function to unveil an unrecognized, essential role for BRD4 in the control of global productive transcriptional elongation. Rapid loss of BRD4 attenuates phosphorylation of the carboxy-terminal domain of RNA polymerase II, independent of genomewide recruitment of CDK9 to promoters, leading to a collapse of the transcriptional core regulatory circuitry. These mechanistic studies are performed in translational models of T-cell acute lymphoblastic leukemia, a disease emblematic for transcriptional addiction, to establish a rationale for human clinical investigation. RNA-Seq for DMSO, dBET6, or JQ1 treated MOLT4 cells
Project description:Goal: study the impact of estrogen receptor (ER) ligands on ER binding to chromatin in MCF-7 cells Methods: ER Chromatin Immunoprecipitation and Sequencing (ChIP-seq) Results: All tested ligands increase binding of ER onto DNA in MCF-7 breast cells. These ligands thus promote an association between ER and DNA, irrespective of their mode of action: selective ER modulator (SERM) 4-OH tamoxifen, and selective ER degraders (SERD) fulvestrant and GDC-0927.
Project description:The role of histone lysine methylation in estrogen receptor-alpha (ERα)-activated transcription is highly context-specific and poorly understood. Here, we show that lysine demethylase 1 (LSD1) mediates loss of H3 lysine 4 dimethylation (H3K4me2) in coordination with tripartite-motif-containing protein 24 (TRIM24)- regulated growth of breaset cancer-derived cells. We performed global profiling of histone H3K4me2 in comparison to genome-wide binding of TRIM24 in MCF7 cells when estrogen is depleted or added. We found specific subsets of genes with functions in transcription and cell proliferation are depleted of H3K4me2 at TRIM24 binding sites. Chromatin immunoprecipitation (ChIP) analyses over a time course of estrogen induction revealed cyclic demethylation of H3K4me2, LSD1, TRIM24 and ERα binding. Inhibition of LSD1 enzymatic activity led to increased H3K4me2 and decreased estrogen response of TRIM24-dependent genes. Additon of a small molecule inhibitor of the TRIM24 bromodomain or depletion of TRIM24 expression amplified the impact of LSD1 inhbition as measured by survival and proliferation of MCF7 cells, suggesting that combinatorial inhibition of LSD1 and TRIM24 may be effective in targeting ER-positive breast cancers.
