Loss of cell cycle checkpoint control and acquisition of the ability to proliferate indefinitely constitute two of the fundamental changes required for the development of cancer. BRIT1 (BRCT-Repeat Inhibitor of hTERT expression), a novel gene identified through our enhanced retroviral mutation screen as a repressor of hTERT function, is implicated in cellular immortalization. Our preliminary data indicate that BRIT1 has additional functions-regulating both the intra-S and G2/M checkpoints-that, in part, may result from its regulation of BRCA1 and Chk1 expression and its direct role in the transmission of DNA damage signals. Moreover, BRIT1 is located on chromosome 8p23.1, which has been implicated in the development of several malignancies, including breast cancer and ovarian cancer, based on LOH and CGH analyses. The expression of BRIT1 also was significantly reduced in these two cancer types when analyzed by DNA arrays. Thus, we hypothesize that BRIT1 may function as a tumor suppressor gene through dual functions: repressing cellular immortalization and maintaining genomic stability. This hypothesis will be tested in the following steps. (1) We will determine the role of BR T1 in preventing cellular immortalization by using normal human cells that conditionally express small hairpin RNA against BRIT1, and we will investigate the mechanisms mediating BRIT1's function on hTERT expression. (2) We will use BRIT 1-depleted cells to study the role of BRIT1 in the response to genotoxic stress, maintenance of genomic integrity, and cellular transformation; we will assess genomic instability by detecting chromosome alterations using comparative genomic hybridization (CGH) and spectral karyotyping (SKY); we will study how BRIT1 regulates the promoter activities of BRCA1 and Chk1 and how BRIT1 may play a direct role in transmission of DNA damage signal; and we will develop a BRIT1 conditional knockout mouse model to assess the BRIT1's function in vivo in maintaining genomic integrity and suppressing tumor formation. (3) We will identify and characterize the aberrations of BRIT1 in breast and ovarian cancer samples to determine if BRIT1 serves as a prognostic marker or as a therapeutic target in cancer. As a corollary, an analysis of the function of BRIT1 and its aberrations in cancer patients will contribute to an improved understanding of the key pathological alterations in cancer initiation and progression and to the development of novel, effective therapeutic approaches for cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA112291-02
Application #
7072663
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Spalholz, Barbara A
Project Start
2005-06-01
Project End
2010-04-30
Budget Start
2006-06-08
Budget End
2007-04-30
Support Year
2
Fiscal Year
2006
Total Cost
$260,360
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Other Basic Sciences
Type
Other Domestic Higher Education
DUNS #
800772139
City
Houston
State
TX
Country
United States
Zip Code
77030
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Pan, Mei-Ren; Hsieh, Hui-Ju; Dai, Hui et al. (2012) Chromodomain helicase DNA-binding protein 4 (CHD4) regulates homologous recombination DNA repair, and its deficiency sensitizes cells to poly(ADP-ribose) polymerase (PARP) inhibitor treatment. J Biol Chem 287:6764-72
Peng, Guang; Yim, Eun-Kyoung; Dai, Hui et al. (2009) BRIT1/MCPH1 links chromatin remodelling to DNA damage response. Nat Cell Biol 11:865-72
Peng, Guang; Lin, Shiaw-Yih (2009) The linkage of chromatin remodeling to genome maintenance: contribution from a human disease gene BRIT1/MCPH1. Epigenetics 4:457-61
Peng, Guang; Lin, Shiaw-Yih (2009) BRIT1/MCPH1 is a multifunctional DNA damage responsive protein mediating DNA repair-associated chromatin remodeling. Cell Cycle 8:3071-2
Rai, Rekha; Phadnis, Ashwini; Haralkar, Sharda et al. (2008) Differential regulation of centrosome integrity by DNA damage response proteins. Cell Cycle 7:2225-33
Rai, Rekha; Peng, Guang; Li, Kaiyi et al. (2007) DNA damage response: the players, the network and the role in tumor suppression. Cancer Genomics Proteomics 4:99-106

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