Maf1 is a novel target of PTEN and PI3K signaling that negatively regulates oncogenesis and lipid metabolism.

Abstract

Maf1 was initially identified as a transcriptional repressor of RNA pol III-transcribed genes, yet little is known about its other potential target genes or its biological function. Here, we show that Maf1 is a key downstream target of PTEN that drives both its tumor suppressor and metabolic functions. Maf1 expression is diminished with loss of PTEN in both mouse models and human cancers. Consistent with its role as a tumor suppressor, Maf1 reduces anchorage-independent growth and tumor formation in mice. PTEN-mediated changes in Maf1 expression are mediated by PTEN acting on PI3K/AKT/FoxO1 signaling, revealing a new pathway that regulates RNA pol III-dependent genes. This regulatory event is biologically relevant as diet-induced PI3K activation reduces Maf1 expression in mouse liver. We further identify lipogenic enzymes as a new class of Maf1-regulated genes whereby Maf1 occupancy at the FASN promoter opposes SREBP1c-mediated transcription activation. Consistent with these findings, Maf1 inhibits intracellular lipid accumulation and increasing Maf1 expression in mouse liver abrogates diet-mediated induction of lipogenic enzymes and triglycerides. Together, these results establish a new biological role for Maf1 as a downstream effector of PTEN/PI3K signaling and reveal that Maf1 is a key element by which this pathway co-regulates lipid metabolism and oncogenesis.

• Authors: Beth M Palian, Aarti D Rohira, Sandra A S Johnson, Lina He, Ni Zheng, Louis Dubeau, Bangyan L Stiles, Deborah L Johnson
• Journal: PLoS genetics (PLoS Genet) Vol. 10 Issue 12 Pg. e1004789 (Dec 2014) ISSN: 1553-7404 [Electronic] United States
• PMID: 25502566 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• FOXO1 protein, human
• Forkhead Box Protein O1
• Forkhead Transcription Factors
• Foxo1 protein, mouse
• MAF1 protein, human
• Maf1 protein, mouse
• Repressor Proteins
• Phosphatidylinositol 3-Kinases
• PTEN Phosphohydrolase
• PTEN protein, human
• Pten protein, mouse

Topics

• Animals
• Carcinogenesis
• Cell Line, Tumor
• Chromatin Immunoprecipitation
• Forkhead Box Protein O1
• Forkhead Transcription Factors (genetics, metabolism)
• Hep G2 Cells
• Humans
• Immunohistochemistry
• Lipid Metabolism (genetics)
• Male
• Mice
• Mice, Inbred C57BL
• Neoplasms (complications, genetics)
• Obesity (complications, genetics)
• PTEN Phosphohydrolase (genetics, metabolism)
• Phosphatidylinositol 3-Kinases (genetics, metabolism)
• Promoter Regions, Genetic
• Repressor Proteins (genetics, metabolism)
• Signal Transduction