Biology subjects

Johannessen, C.

Publications and source records attributed to Johannessen, C..

2 recordsLinked to original sources

bioRxiv2025

Targeted Transcriptional Repression by Induced Proximity

Most cancer-driving proteins remain "undruggable" due to the absence of ligandable pockets and their reliance on intrinsically disordered or protein-DNA/protein-protein interactions. Transcription factors, which orchestrate oncogenic gene expression programs, are particularly challenging: they turn over rapidly, evade durable pharmacological inhibition, and resist even emerging targeted protein degradation strategies. Here, we describe a new induced-proximity therapeutic modality, Transcriptional Regulation via Active Control of Epigenetic Reprogramming (TRACER), that enforces locus-specific transcriptional silencing by recruiting endogenous corepressor complexes to transcription factor binding sites. We developed small-molecule TRACERs that tether methyl-CpG binding domain protein 2 (MBD2) and the Nucleosome Remodeling and Deacetylase (NuRD) complex to transcription factor-directed ligands. An estrogen receptor (ER) TRACER potently suppressed ER transcriptional activity in breast cancer cells, downregulated canonical ER target genes, and required MBD2 and histone deacetylase (HDAC1/2) for activity, confirming on-target epigenetic repression. Extending this approach to prostate cancer, an androgen receptor (AR) TRACER transcriptionally repressed both full-length AR and the drug-resistant truncation variant AR-V7, achieving >90% inhibition of AR transcriptional activity in androgen-independent prostate cancer cells with locus-specific gene repression. We further show that TRACERs can be modularly reprogrammed to recruit alternative repressors, including PRC2. Collectively, these findings establish TRACERs as a generalizable modality to pharmacologically silence undruggable transcription factors through targeted epigenetic reprogramming, offering a powerful new strategy for treating cancers refractory to existing therapies.

biochemistry↗

bioRxiv2021

Use of Raman and Raman optical activity to extract atomistic details of saccharides in aqueous solution

Sugars are crucial components in biosystems and industrial applications. In aqueous environments, the natural state of short saccharides or charged glycosaminoglycans is floating and wiggling in solution. Therefore, tools to characterize their structure in a native aqueous environment are crucial but not always available. Here, we show that a combination of Raman/ROA and, on occasions, NMR experiments with Molecular Dynamics (MD) and Quantum Mechanics (QM) is a viable method to gain insights into structural features of sugars in solutions. Combining these methods provides information about accessible ring puckering conformers and their proportions. It also provides information about the conformation of the linkage between the sugar monomers, i.e., glycosidic bonds, allowing for identifying significantly accessible conformers and their relative abundance. For mixtures of sugar moieties, this method enables the deconvolution of the Raman/ROA spectra to find the actual amounts of its molecular constituents, serving as an effective analytical technique. For example, it allows calculating anomeric ratios for reducing sugars and analyzing more complex sugar mixtures to elucidate their real content. Altogether, we show that combining Raman/ROA spectroscopies with simulations is a versatile method applicable to saccharides. It allows for accessing many features with precision comparable to other methods routinely used for this task, making it a viable alternative. Furthermore, we prove that the proposed technique can scale up by studying the complicated Raffinose trisaccharide, and therefore, we expect its wide adoption to characterize sugar structural features in solution.

biophysics↗