IRF1 suppresses Ki-67 promoter activity through interfering with Sp1 activation

Interferon regulatory factor 1 (IRF1) shows tumor-suppressor activity by suppressing proliferation of cancer cells. To exert its anti-proliferative effects, this factor must ultimately control transcription of several key genes that regulate cell cycle progression. Here, we showed that Ki-67 gene is...

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Veröffentlicht in:Tumor biology 2012-12, Vol.33 (6), p.2217-2225
Hauptverfasser: Chen, Feifei, Song, Jian, Di, Jiehui, Zhang, Qing, Tian, Hui, Zheng, Junnian
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Sprache:eng
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Zusammenfassung:Interferon regulatory factor 1 (IRF1) shows tumor-suppressor activity by suppressing proliferation of cancer cells. To exert its anti-proliferative effects, this factor must ultimately control transcription of several key genes that regulate cell cycle progression. Here, we showed that Ki-67 gene is a novel proliferation-related downstream target of IRF1. IRF1 repressed Ki-67 gene transcription in a dose-dependent manner in human Ketr-3 and 786-O renal carcinoma cells. We previously cloned the Ki-67 core promoter which contained two functional Sp1 binding sites. Mutation of the two Sp1 binding sites abrogated Sp1-dependent enhancement of Ki-67 promoter activity. Forced elevation of IRF1 decreased endogenous Sp1 protein level. However, there was no effect on Sp1 mRNA level after transfected with IRF1. Our findings establish a casual series of events that connect anti-proliferative effects of IRF1 with the Ki-67 gene, which encodes a key regulator of the G1/S phase transition. It suggests that the inhibitory effect on Ki-67 gene expression mediated by decreasing level of Sp1 protein might be a novel function of the anti-tumor activity of IRF1.
ISSN:1010-4283
1423-0380
DOI:10.1007/s13277-012-0483-3