Biology subjects

Niskanen, E. A.

Publications and source records attributed to Niskanen, E. A..

3 recordsLinked to original sources

bioRxiv2024

Steroid receptor-assisted loading modulates transcriptional responses in prostate cancer cells

Steroid receptors are involved in a wide array of crosstalk mechanisms that regulate diverse biological processes, with significant implications in diseases, particularly in cancers. In prostate cancer, indirect crosstalk between androgen receptor (AR) and glucocorticoid receptor (GR) is well-documented, wherein AR suppression by antiandrogen therapy leads to elevated GR levels, enabling GR to compensate for and replace AR signaling. However, the existence and impact of direct chromatin crosstalk between AR and GR in prostate cancer have remained elusive. Our genome-wide investigations reveal that AR activation significantly expands GR chromatin binding. Mechanistically, AR induces remodeling of closed chromatin sites, facilitating GR binding to inaccessible sites. Importantly, coactivation of AR and GR results in distinct transcriptional responses at both the cell population and single-cell levels. Intriguingly, pathways affected by these transcriptional changes are generally associated with improved patient survival. Thus, the direct crosstalk between AR and GR yields markedly different outcomes from the known role of GR in circumventing AR blockade by antiandrogens.

genomics↗

bioRxiv2024

KMAP: Kmer Manifold Approximation and Projection for visualizing DNA sequences

Identifying and illustrating patterns in DNA sequences is a crucial task in various biological data analyses. In this task, patterns are often represented by sets of kmers, the fundamental building blocks of DNA sequences. To visually unveil these patterns, we could project each kmer onto a point in two-dimensional (2D) space. However, this projection poses challenges due to the high-dimensional nature of kmers and their unique mathematical properties. Here, we established a mathematical system to address the peculiarities of the kmer manifold. Leveraging this kmer manifold theory, we developed a statistical method named KMAP for detecting kmer patterns and visualizing them in 2D space. We applied KMAP to three distinct datasets to showcase its utility. KMAP achieved a comparable performance to the classical method MEME, with approximately 90% similarity in motif discovery from HT-SELEX data. In the analysis of H3K27ac ChIP-seq data from Ewing Sarcoma (EWS), we found that BACH1, OTX2 and ERG1 might affect EWS prognosis by binding to promoter and enhancer regions across the genome. We also found that FLI1 bound to the enhancer regions after ETV6 degradation, which showed the competitive binding between ETV6 and FLI1. Moreover, KMAP identified four prevalent patterns in gene editing data of the AAVS1 locus, aligning with findings reported in the literature. These applications underscore that KMAP could be a valuable tool across various biological contexts. KMAP is freely available at: https://github.com/chengl7-lab/kmap.

bioinformatics↗

bioRxiv2023

Chromatin Accessibility and Pioneer Factor FOXA1 Shape Glucocorticoid Receptor Action in Prostate Cancer

Treatment of prostate cancer relies predominantly on the inhibition of androgen receptor (AR) signaling. Despite the initial effectiveness of the antiandrogen therapies, the cancer often develops resistance to the AR blockade. One mechanism of the resistance is glucocorticoid receptor (GR)-mediated replacement of AR function. Nevertheless, the mechanistic ways and means how the GR-mediated antiandrogen resistance occurs have remained elusive. Here, we have discovered several crucial features of GR action in prostate cancer cells through genome-wide techniques. We detected that the replacement of AR by GR in enzalutamide-exposed prostate cancer cells occurs almost exclusively at pre-accessible chromatin sites displaying FOXA1 occupancy. Counterintuitively to the classical pioneer factor model, silencing of FOXA1 potentiated the chromatin binding and transcriptional activity of GR. This was attributed to FOXA1-mediated repression of the NR3C1 (gene encoding GR) expression via the corepressor TLE3. Moreover, the small-molecule inhibition of coactivator p300s enzymatic activity efficiently restricted GR-mediated gene regulation and cell proliferation. Overall, we identified chromatin pre-accessibility and FOXA1-mediated repression as important regulators of GR action in prostate cancer, pointing out new avenues to oppose steroid receptor-mediated antiandrogen resistance.

molecular biology↗