Investigating the role of cholesterol in WT1/BASP1-mediated gene regulation

  • Anna F Fleming

Student thesis: Master's ThesisMaster of Science (MSc)

Abstract

Brain Acid Soluble Protein 1 (BASP1) is a transcriptional co-suppressor of Wilms’ Tumour Suppressor Protein (WT1). Previous work by our group has shown that BASP1 binds cholesterol through a cholesterol recognition amino acid consensus motif (CRAC motif) and has indicated that cholesterol binding by BASP1 may be necessary for its gene-repressive activity at some target genes. BASP1 represses transcription in chronic myelogenous leukaemia (K562) cells by mediating removal of activating histone marks including acetyl-histone 3 lysine 9 (H3K9Ac) and trimethyl-histone 3 lysine 4 (H3K4Me3). Removal of these marks is dependent on an intact CRAC motif in BASP1.
In this study, the role of cholesterol in WT1/BASP1-mediated gene repression was investigated using treatment of cultured cells with atorvastatin, an inhibitor of cholesterol biosynthesis, followed by RNA analysis and chromatin immunoprecipitation (ChIP). In order to identify any cell type-specific effects, analyses were carried out in K562 cells and the breast cancer line MCF-7. The findings show that treatment of either cell type with atorvastatin can alter the function of BASP1. The results confirm that WT1/BASP1-mediated gene repression in K562 cells involves removal of H3K4Me3 and H3K9Ac and find that these events also occur in MCF-7 cells. Furthermore, treatment of either cell type with atorvastatin inhibits BASP1-dependent removal of H3K4Me3 and H3K9Ac.
Several previous studies have identified a tumour suppressive role of BASP1. During this work, the tumorigenicity of K562 and MCF-7 cells was investigated in order to determine if BASP1-dependent tumour suppression withstood cholesterol depletion. In both K562 and MCF-7 cells, treatment with atorvastatin reduced tumorigenicity, but evidence of a BASP1-dependent change was inconclusive.
The results indicate that cholesterol is necessary for WT1/BASP1-mediated H3K9Ac and H3K4Me3 removal, resulting in transcriptional repression of target genes. This confirms and expands upon previous work which identifies a novel role for cholesterol in gene regulation.
Date of Award23 Jan 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorStefan G E Roberts (Supervisor)

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