PML nuclear bodies contribute to the basal expression of the mTOR inhibitor DDIT4.
The promyelocytic leukemia (PML) protein is an essential component of PML nuclear bodies (PML NBs) frequently lost in cancer. PML NBs coordinate chromosomal regions via modification of nuclear proteins that in turn may regulate genes in the vicinity of these bodies. However, few PML NB-associated genes have been identified. PML and PML NBs can also regulate mTOR and cell fate decisions in response to cellular stresses. We now demonstrate that PML depletion in U2OS cells or TERT-immortalized normal human diploid fibroblasts results in decreased expression of the mTOR inhibitor DDIT4 (REDD1). DNA and RNA immuno-FISH reveal that PML NBs are closely associated with actively transcribed DDIT4 loci, implicating these bodies in regulation of basal DDIT4 expression. Although PML silencing did reduce the sensitivity of U2OS cells to metabolic stress induced by metformin, PML loss did not inhibit the upregulation of DDIT4 in response to metformin, hypoxia-like (CoCl2) or genotoxic stress. Analysis of publicly available cancer data also revealed a significant correlation between PML and DDIT4 expression in several cancer types (e.g. lung, breast, prostate). Thus, these findings uncover a novel mechanism by which PML loss may contribute to mTOR activation and cancer progression via dysregulation of basal DDIT4 gene expression.
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Jayme
J
Salsman
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Alex
A
Stathakis
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Ellen
E
Parker
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Dudley
D
Chung
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Livia E
LE
Anthes
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Kara L
KL
Koskowich
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.
Sara
S
Lahsaee
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.|Department of Pathology and Laboratory Medicine, Nova Scotia Health Authority, Halifax, Nova Scotia, B3H 1V8, Canada.
Daniel
D
Gaston
Departments of Genetics and Pathology, Stanford University, Stanford, California, 94305, USA.
Kimberly R
KR
Kukurba
Departments of Genetics and Pathology, Stanford University, Stanford, California, 94305, USA.
Kevin S
KS
Smith
Atlantic Cancer Research Institute, Moncton, New Brunswick, E1C 8X3, Canada.
Ian C
IC
Chute
Atlantic Cancer Research Institute, Moncton, New Brunswick, E1C 8X3, Canada.
Daniel
D
Léger
Atlantic Cancer Research Institute, Moncton, New Brunswick, E1C 8X3, Canada.
Laura D
LD
Frost
Departments of Genetics and Pathology, Stanford University, Stanford, California, 94305, USA.
Stephen B
SB
Montgomery
Atlantic Cancer Research Institute, Moncton, New Brunswick, E1C 8X3, Canada.|Department of Microbiology &Immunology, Dalhousie University, Halifax Nova Scotia, B3H 4R2, Canada.|Department of Chemistry &Biochemistry, Université de Moncton, Moncton, New Brunswick, E1A 3E9, Canada.|Department of Biology, University of New Brunswick, Saint John, New Brunswick, E2L 4L5, Canada.
Stephen M
SM
Lewis
Department of Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, S7N5A8, Canada.
Christopher
C
Eskiw
Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.|Department of Biochemistry &Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.|Beatrice Hunter Cancer Research Institute, Halifax, Nova Scotia, B3H 4R2, Canada.
Graham
G
Dellaire
D045744:Cell Line, Tumor; D003035:Cobalt / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D055786:Gene Knockout Techniques; D020868:Gene Silencing; D056426:Genetic Loci; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D011839:Radiation, Ionizing; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
C469991:DDIT4 protein, human; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D003035:Cobalt; D058570:TOR Serine-Threonine Kinases; C018021:cobaltous chloride