The oncoprotein HBXIP activates transcriptional coregulatory protein LMO4 via Sp1 to promote proliferation of breast cancer cells.

Abstract

Hepatitis B X-interacting protein (HBXIP) is an important oncoprotein that plays critical role in the development of cancer. In this study, we report that HBXIP activates LIM-only protein 4 (LMO4), a transcriptional coregulatory protein, in promotion of cell proliferation. We observed that the messenger RNA (mRNA) expression levels of HBXIP were positively associated with those of LMO4 in clinical breast cancer tissues. We further identified that HBXIP upregulated LMO4 at the levels of promoter, mRNA and protein in MCF-7 and LM-MCF-7 breast cancer cell lines. The expression of cyclin D1 and cyclin E, downstream effectors of LMO4, could be upregulated by HBXIP through LMO4. Then, chromatin immunoprecipitation (ChIP) assay revealed that HBXIP was able to interact with the promoter region of LMO4. Electrophoretic mobility shift assay showed that HBXIP occupied the -237/-206 region of LMO4 promoter containing Sp1 binding element. The mutant of Sp1 binding site in the LMO4 promoter impeded the interaction of HBXIP with the promoter. Co-immunoprecipitation, ChIP and luciferase reporter gene assays showed that HBXIP activated LMO4 promoter through binding to Sp1. In function, flow cytometry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays and animal transplantation assays demonstrated that HBXIP-enhanced cell proliferation of breast cancer through upregulating LMO4 in vitro and in vivo. Thus, we concluded that oncoprotein HBXIP is able to activate the transcriptional coregulatory protein LMO4 through transcription factor Sp1 in promotion of proliferation of breast cancer cells. HBXIP may serve as a driver gene to activate transcription in the development of cancer.

• Authors: Lin Yue, Leilei Li, Fangfang Liu, Nan Hu, Weiying Zhang, Xiao Bai, Yinghui Li, Yingyi Zhang, Li Fu, Xiaodong Zhang, Lihong Ye
• Journal: Carcinogenesis (Carcinogenesis) Vol. 34 Issue 4 Pg. 927-35 (Apr 2013) ISSN: 1460-2180 [Electronic] England
• PMID: 23291272 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• Cyclin E
• LAMTOR5 protein, human
• LIM Domain Proteins
• LMO4 protein, human
• RNA, Messenger
• RNA, Small Interfering
• Sp1 Transcription Factor
• Cyclin D1

Topics

• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Animals
• Breast Neoplasms (genetics, metabolism)
• Cell Line, Tumor
• Cell Proliferation
• Chromatin Immunoprecipitation
• Cyclin D1 (biosynthesis)
• Cyclin E (biosynthesis)
• Disease Progression
• Electrophoretic Mobility Shift Assay
• Female
• Gene Expression Regulation, Neoplastic
• Humans
• LIM Domain Proteins (genetics, metabolism)
• MCF-7 Cells
• Mice
• Mice, Inbred BALB C
• Promoter Regions, Genetic
• RNA Interference
• RNA, Messenger
• RNA, Small Interfering
• Sp1 Transcription Factor (genetics, metabolism)
• Transcription, Genetic