Chromatin changes on the GSTP1 promoter associated with its inactivation in prostate cancer.
Glutathione-S-transferases (GSTs) are metabolic enzymes that help detoxify and eliminate harmful chemicals. In prostate tumors, expression of GST pi (encoded by GSTP1) is frequently lost because of promoter hypermethylation. Here we analyze the native GSTP1 promoter in cancerous and noncancerous human prostate cells to identify structural features associated with its cancer-related transcriptional silencing. We find that in noncancerous prostate cells (RWPE-1 and PWR-1E) GSTP1 is constitutively expressed, not methylated, highly accessible, bound by transcription factors and associated with histones with activating modifications (histone H3 methylated at lysine 4 and acetylated histones H3 and H4). In contrast, in cancerous prostate cells (LNCaP) GSTP1 is not expressed, extensively methylated, inaccessible, lacks bound transcription factors and is not associated with histones with activating modifications. We do not detect significant levels of histones with repressive modifications (histone H3 methylated at lysine 9 or 27) on GSTP1 in any cell line indicating that they are not associated with cancer-related GSTP1 silencing. Treatment of LNCaP cells with 5-azacytidine restores activating histone modifications on GSTP1 and reactivates transcription. We conclude that, in the process of prostate carcinogenesis, activating histone modifications on GSTP1 are lost and the DNA becomes methylated and inaccessible resulting in transcriptional silencing.
Okino
Steven T
ST
Department of Urology, San Francisco Veterans Affairs Medical Center and the University of California San Francisco, San Francisco, California 94121, USA.
Pookot
Deepa
D
Majid
Shahana
S
Zhao
Hong
H
Li
Long-Cheng
LC
Place
Robert F
RF
Dahiya
Rajvir
R
D001483:Base Sequence; D002843:Chromatin / Q000648:ultrastructure*; D020868:Gene Silencing; D051549:Glutathione S-Transferase pi / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics*; D046509:Tissue Culture Techniques
D002843:Chromatin; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi