ACTR/AIB1 Functions as an E2F1 Coactivator To Promote Breast Cancer Cell Proliferation and Antiestrogen Resistance

Authors

Maggie C. Louie, Department of Biological Chemistry, School of Medicine, UCD Cancer Center/Basic Science, University of California at DavisFollow
June X. Zou, Department of Biological Chemistry, School of Medicine, UCD Cancer Center/Basic Science, University of California at DavisFollow
Alina Rabinovich, Department of Biological Chemistry, School of Medicine, UCD Cancer Center/Basic Science, University of California at Davis
Hong-Wu Chen, Department of Biological Chemistry, School of Medicine, UCD Cancer Center/Basic Science, University of California at DavisFollow

Document Type

Article

Source

Molecular and Cellular Biology

ISSN

0270-7306

Volume

24

Issue

12

First Page

5157

Last Page

5171

Publication Date

2004

Department

Natural Sciences and Mathematics

Abstract

Overexpression or amplification of ACTR (also named AIB1, RAC3, p/CIP, TRAM-1, and SRC-3), a member of the p160 family of coactivators for nuclear hormone receptors, has been frequently detected in multiple types of human tumors, including breast cancer. However, its role in cancer cell proliferation and the underlying mechanism are unclear. Here, we show that overexpression of ACTR not only enhances estrogen-stimulated cell proliferation but also, more strikingly, completely negates the cell cycle arrest effect by tamoxifen and pure antiestrogens. Unexpectedly, we found that ACTR directly interacts, through its N-terminal domain, with E2F1 and is recruited to E2F target gene promoters. Elevation of ACTR in quiescent cells strongly stimulates the transcription of a subset of E2F-responsive genes that are associated with the G1/S transition. We also demonstrated, by adenovirus vector-mediated RNA interference, that ACTR is required for E2F1-mediated gene expression and the proliferation of estrogen receptor (ER)-negative breast cancer cells. Moreover, the ability of elevated ACTR to promote estrogen-independent cell proliferation depends on the function of E2F1 and the association between ACTR and E2F1, but not ER. Thus, our results reveal an essential role of ACTR in control of breast cancer cell proliferation and implicate the ACTR-E2F1 pathway as a novel mechanism in antiestrogen resistance.

Rights

Copyright © 2004 American Society for Microbiology. All rights reserved.

PubMed ID

15169882