Fischer, Sandra (2020)
Auto- and cross-regulation of the hnRNPs D and DL & Hypoxia-driven gene expression changes in human cancer cells.
Technische Universität Darmstadt
doi: 10.25534/tuprints-00009139
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

RNA-binding proteins (RBPs) control all steps of mRNA processing, including pre-mRNA splicing, mRNA localization, stability and translation efficiency. Auto- and cross-regulation of RBPs is essential for RBP homeostasis and the prevention of pathologies. Consequently, deregulation of RBPs is prevalent in diseases, in particular during tumorigenesis. A profound understanding of RBP regulation is thus indispensible to open up new approaches in cancer therapy. HnRNP DL is a ubiquitous RBP that is overexpressed in prostate cancer and chronic myeloid leukemia. HnRNP DL was suggested to regulate its own expression in a negative feedback loop via usage of a poison exon in its 3’ UTR. In this study, hnRNP DL autoregulation by binding to its own pre-mRNA was confirmed and cross-regulation between hnRNP DL and its well-studied paralog hnRNP D (AUF1) was demonstrated. Strikingly, hnRNP DL is a crucial factor for endothelial cell function, such as migration and angiogenesis. This highlights the influence of hnRNP DL, and RBPs in general, on cellular key processes. The cellular environment has an influence on the levels of RBPs and their functionality. Oxygen starvation (hypoxia) is a common cellular stress. It appears physiologically at high altitudes or during embryonic development, but hypoxia is also typical for diseased tissue. In particular in solid tumors, the hypoxic microenvironment influences gene expression and promotes cancerogenesis leading to poor patient outcomes. The transcriptional response to hypoxia is well studied and controlled by hypoxia inducible factor (HIF) proteins. However, the posttrancriptional response to hypoxia is still poorly understood. Thus, this study focused on hypoxia-driven changes in RBP levels and alternative splicing (AS) in human cancer cells. Transcriptome analyses showed correlated gene expression changes in human lung and breast cancer cells after chronic hypoxia treatment, but AS changes were highly divergent, demonstrating the cell type-specificity of AS. Strikingly, muscleblind-like 2 (MBNL2) was specifically induced under hypoxia, while RBPs were predominantly reduced. Subsequent transcriptome analyses after MBNL2 depletion showed that MBNL2 controls hypoxia-driven AS and the transcript abundance of typical hypoxia-induced genes, such as vascular endothelial growth factor (VEGFA). Strikingly, this control is specific for MBNL2 and not shared by its paralog MBNL1, showing the importance of MBNL2 for cancer cell adaptation to hypoxia. In addition, MBNL2 depletion led to reduced cancer cell proliferation and migration, indicating that deregulated RBPs might be new targets for cancer therapy.

Frage zum Eintrag

Redaktionelle Details anzeigen