Regulation of protein kinase CbetaII (PKCbetaII) gene expression in chronic lymphocytic leukaemia (CLL) cells

Al-Sanabra, Ola Regulation of protein kinase CbetaII (PKCbetaII) gene expression in chronic lymphocytic leukaemia (CLL) cells. PhD thesis, University of Liverpool.

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Abstract

Chronic lymphocytic leukaemia (CLL) cells are derived from mature B lymphocytes and are distinctive with respect to overexpression of the classical protein kinase C isoform protein kinase CβII (PKCβII), which is encoded by PRKCB. Expression of PKCβII in CLL plays a vital role in the pathogenesis of the malignant cells in this disease, and within the microenvironment cells where it provides signals for the production of factors which support the survival of CLL cells. In CLL cells PRKCB transcription is stimulated by vascular endothelial growth factor (VEGF) through a mechanism involving activated PKCβII. However, at the beginning of this thesis the molecular regulatory mechanism(s) governing expression of the PKCβ gene were poorly described. Thus, to characterise the factors regulating PRKCB transcription in CLL cells I used different approaches including mithramycin treatment, a drug which intercalates into GC-rich areas of DNA to inhibit binding of specificity protein 1 (Sp1), specific Sp1 siRNA, promoter function assays and site directed mutagenesis and chromatin immunoprecipitation (ChIP). Experiments using these techniques showed that Sp1 has a direct role in driving expression of the gene coding for PKCβII in CLL cells. My results also show that Sp1 is highly associated with the PRKCB promoter in CLL cells compared to that in normal B cells, and suggest that this is likely because of the presence of histone marks permissive of gene activation. Examination of other transcription factors such as Sp3, MITF, RUNX1 and E2F1 that potentially bind the PRKCB promoter showed that they have static or indirect effects in regulating transcription of this gene. The exception to this is STAT3 which my data suggests plays a role in suppressing PKCβ gene expression in CLL cells. Exploration of the mechanism through which VEGF induces PRKCB transcription revealed that this growth factor stimulates increased association of Sp1 and decreased association of STAT3 with the PRKCB promoter. Thus, VEGF-stimulated activation of PKCβII may play a role in this process. Taken together, Sp1 is the major driver for overexpression of PKCβII in CLL cells, and because this transcription factor is also overexpressed in these cells, the mechanisms I describe controlling PRKCB transcription potentially provide a foundation for further study of other genes contributing to the phenotype of CLL cells that are regulated by this pleiotropic transcription factor.

Item Type:	Thesis (PhD)
Additional Information:	Date: 2015-07 (completed)
Subjects:	?? RC0254 ??
Depositing User:	Symplectic Admin
Date Deposited:	09 Dec 2015 16:57
Last Modified:	17 Dec 2022 01:31
DOI:	10.17638/02025339
URI:	https://livrepository.liverpool.ac.uk/id/eprint/2025339