Identification of nuclear localization signal that governs nuclear import of BRD7 and its essential roles in inhibiting cell cycle progression.
BRD7, a novel bromodomain gene, is identified to be associated with nasopharyngeal carcinoma (NPC). Decreased or loss of expression of BRD7 was detected in NPC biopsies and cell lines. Overexpression of BRD7 could inhibit NPC cell growth and arrest cells in cell cycle by transcriptionally regulating some important molecules involved in ras/MEK/ERK and Rb/E2F pathway, and downregulate the promoter activity of E2F3. In the present study, the subcellular localization of BRD7 was investigated. It was found that BRD7 was mainly localized in nucleus without distinct cell-specific difference between COS7 and HNE1. Furthermore, a functional nuclear localization signal (NLS) sequence ranging from amino acid 65 to 96 was identified and characterized. The NLS is composed of a cluster of four bipartite nuclear targeting sequences, which are tightly linked and extremely overlapped. We found that whether the entire NLS or the four bipartite nuclear targeting sequences could respectively determine the nuclear import of green fluorescent protein (GFP). The most important is that NLS-deleted BRD7 shifted the nuclear localization to be mostly in cytoplasm, and failed or reduced to negatively regulate the expression of cell cycle related molecules, cyclin D1 and E2F3, and cell cycle progression from G1 to S phase. In conclusion, NLS is an essential motif affecting BRD7 nuclear distribution, and the nuclear localization of BRD7 is critical for the expression of cell cycle related molecules and cell biological function.
Zhou
Ming
M
Cancer Research Institute, Central South University Xiang-Ya School of Medicine, 110 Xiang-Ya Road, Changsha, Hunan 410078, China.
Liu
Huaying
H
Xu
Xiaojie
X
Zhou
Houde
H
Li
Xiaoling
X
Peng
Cong
C
Shen
Shourong
S
Xiong
Wei
W
Ma
Jian
J
Zeng
Zhaoyang
Z
Fang
Songqing
S
Nie
Xinmin
X
Yang
Yixin
Y
Zhou
Jie
J
Xiang
Juanjuan
J
Cao
Li
L
Peng
Shuping
S
Li
Shufang
S
Li
Guiyuan
G
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D050699:E2F3 Transcription Factor / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000502:physiology*; D000092468:Bromodomain Containing Proteins
D002868:Chromosomal Proteins, Non-Histone; D019938:Cyclin D1; D050699:E2F3 Transcription Factor; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; C485694:BRD7 protein, human; D000092468:Bromodomain Containing Proteins; C098319:E2F3 protein, human