The transcriptional coregulator RIP140 represses E2F1 activity and discriminates breast cancer subtypes.
OBJECTIVE
Receptor-interacting protein of 140 kDa (RIP140) is a transcriptional cofactor for nuclear receptors involved in reproduction and energy homeostasis. Our aim was to investigate its role in the regulation of E2F1 activity and target genes both in breast cancer cell lines and in tumor biopsies.


METHODS
Glutathione S-transferase pull-down assays, coimmunoprecipitation experiments, and chromatin immunoprecipitation analysis were used to evidence interaction between RIP140 and E2F1. The effects of RIP140 expression on E2F1 activity were determined using transient transfection and quantification of E2F target mRNAs by quantitative real-time PCR. The effect on cell cycle was assessed by fluorescence-activated cell sorting analysis on cells overexpressing green fluorescent protein-tagged RIP140. A tumor microarray data set was used to investigate the expression of RIP140 and E2F1 target genes in 170 breast cancer patients.


RESULTS
We first evidenced the complex interaction between RIP140 and E2F1 and showed that RIP140 represses E2F1 transactivation on various transiently transfected E2F target promoters and inhibits the expression of several E2F1 target genes (such as CCNE1 and CCNB2). In agreement with a role for RIP140 in the control of E2F activity, we show that increasing RIP140 levels results in a reduction in the proportion of cells in S phase in various human cell lines. Finally, analysis of human breast cancers shows that low RIP140 mRNA expression was associated with high E2F1 target gene levels and basal-like tumors.


CONCLUSIONS
This study shows that RIP140 is a regulator of the E2F pathway, which discriminates luminal- and basal-like tumors, emphasizing the importance of these regulations for a clinical cancer phenotype.
Docquier
Aurélie
A
IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France.
Harmand
Pierre-Olivier
PO
Fritsch
Samuel
S
Chanrion
Maïa
M
Darbon
Jean-Marie
JM
Cavaillès
Vincent
V
D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002453:Cell Cycle; D045744:Cell Line, Tumor; D050687:E2F1 Transcription Factor / Q000037:antagonists & inhibitors*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018295:Neoplasms, Basal Cell / Q000235:genetics*; D056971:Nuclear Receptor Co-Repressor 1 / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
D050687:E2F1 Transcription Factor; D056971:Nuclear Receptor Co-Repressor 1
Oncogene. 2006 Aug 28;25(38):5210-9
16936739
Mol Endocrinol. 2006 Jul;20(7):1506-18
16527872
J Natl Cancer Inst. 2006 Feb 15;98(4):262-72
16478745
Mol Cell Biol. 2004 Jun;24(12):5157-71
15169882
Nat Cell Biol. 2000 Apr;2(4):232-9
10783242
J Clin Invest. 2007 Jan;117(1):218-28
17160137
Nat Med. 2000 Dec;6(12):1368-74
11100122
Oncogene. 2006 Aug 28;25(38):5190-200
16936737
EMBO J. 2007 Sep 5;26(17):3968-80
17690688
Genes Dev. 2004 Dec 1;18(23):2952-62
15574596
Biochim Biophys Acta. 2002 Jun 21;1602(2):131-50
12020800
EMBO J. 2000 Feb 15;19(4):662-71
10675335
Curr Mol Med. 2006 Nov;6(7):739-48
17100600
J Biol Chem. 2004 Apr 9;279(15):15645-51
14736873
Proc Natl Acad Sci U S A. 2003 Jul 8;100(14):8418-23
12829800
Exp Biol Med (Maywood). 2006 Jul;231(7):1271-81
16816134
Nature. 1992 Sep 24;359(6393):295-300
1406933
Clin Cancer Res. 2008 Mar 15;14(6):1744-52
18347175
Curr Pharm Biotechnol. 2004 Oct;5(5):459-70
15544494
Proc Natl Acad Sci U S A. 1996 Jan 23;93(2):679-84
8570615
Nucl Recept Signal. 2006 Oct 30;4:e024
17088940
Trends Endocrinol Metab. 2006 Aug;17(6):243-50
16815031
Nucleic Acids Res. 2004 Apr 01;32(6):1957-66
15060175
J Clin Oncol. 2006 Apr 10;24(11):1656-64
16505416
Mol Cell Biol. 1998 Jun;18(6):3212-22
9584162
Breast Cancer Res. 2006;8(2):R23
16626501
Mol Cancer Res. 2003 Nov;1(13):948-58
14638867
Mol Endocrinol. 2001 Apr;15(4):501-11
11266503
Mol Pharmacol. 2006 Apr;69(4):1338-46
16391242
Curr Opin Cell Biol. 2007 Dec;19(6):649-57
18032011
BMC Genomics. 2006 Apr 27;7:96
16643655