SUMOylation in the Regulation of Androgen Receptor and Pioneer Factor FOXA1 in Prostate Cancer Cells
Year: 2015
Type: dissertation
Abstract: Reversible and covalent post-translational modification (PTM) of proteins by small ubiquitin-related modifier (SUMO-1, -2, and -3) is an essential process occurring in all mammals.SUMOylation can affect the target protein´s localization as well as its interactions, stability and activity and in that way it has a regulatory role in many biological functions, including transcription, DNA repair and replication.The androgen receptor (AR) is a well known SUMO target.The AR is a transcription factor (TF) that mediates the effects of androgenic hormones at the level of gene regulation.These androgen-regulated genes are critical in the development and maintenance of the male sexual phenotype, thus they influence the prostate gland.Prostate cancer (PCa) is a serious health concern of men and it i s str on gl y d epen d en t on AR si gn alin g.Thu s, th e AR i s a major d ru ggabl e tar get in advanced PCa.The aim of this thesis was to study the role of SUMO-modification on ARdependent transcription in the natural chromatin environment in PCa cells.Due to its c o o p e r a t i v e r o l e w i t h A R , F O X A 1 h a s b e e n e x t e n s i v e l y s t u d i e d a n d l i n k e d t o P C a development.However, surprisingly little is known about the PTMs of FOXA1, and thus one aim was to study the impact of the SUMO-modification on FOXA1 function.In this thesis, genome-wide gene expression analyses with stable PCa cell lines expressing wildtype AR (wt-AR) or SUMOylation-deficient AR (AR-2KR) revealed that SUMOylation modulates the AR function in a target gene and pathway selective manner.Moreover, genome-wide AR binding analyses (ChIP-seq) indicated that SUMOylation could regulate the AR´s chromatin occupancy, which may partially explain the differential expression between the wtAR and AR-2KR cells on many target loci.The difference in enriched motifs in de novo motif analyses indicated that SUMOylation may regulate the interactions of the A R w i t h o t h e r T F s , i n c l u d i n g F O X A 1 .I n P C a c e l l s , t h e l e v e l o f e n d o g e n o u s A R SUMOylation, SUMO2/3 conjugation in particular, was enhanced by androgens or cell stress.In addition, cell stress altered AR´s intranuclear distribution and detached the AR from chromatin, repressing AR-dependent transcription in a reversible manner.These results suggest that cell stress-induced SUMO-2/3 modifications can protect the AR from misfolding and degradation, whereas the basal level modifications are linked to the activity c y c l e s o f t h e h o r m o n e -b o u n d r e c e p t o r i n t h e n u c l e u s .F O X A 1 i s S U M O y l a t e d a n d S U M O y l a t i o n m o d u l a t e d b o t h A R a n d F O X A 1 ś s t a b i l i t y a n d n u c l e a r m o b i l i t y .Additionally, SUMOylation seemed to enhance FOXA1´s chromatin occupancy and transcriptional activity, which modulated the ability of FOXA1 to collaborate with the AR.In summary, this thesis has yielded new information concerning how SUMOylation of the AR and FOXA1 modulates androgen-regulated gene expression in PCa cells.These results could provide, in the long run, new prospects for PCa therapy.
Author: Päivi Sutinen
Language: English
Subfield: Cancer Research
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2556890072