RESUMO
The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell-fate decision, including cell-cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue-specific tumor suppressor or oncogene. Here, we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and show that pVHL depletion in colorectal cancer cells leads to cell-cycle arrest concomitant with increased transcription of the KLF4-dependent p21 gene. Finally, immunohistochemical staining revealed elevated pVHL and reduced KLF4 levels in colon cancer tissues. We therefore propose that unexpectedly pVHL, via the degradation of KLF4, is a facilitating factor in colorectal tumorigenesis.
Assuntos
Neoplasias Colorretais/genética , Fatores de Transcrição Kruppel-Like/metabolismo , Proteína Supressora de Tumor Von Hippel-Lindau/fisiologia , Linhagem Celular Tumoral , Proliferação de Células , Transformação Celular Neoplásica , Neoplasias Colorretais/metabolismo , Inibidor de Quinase Dependente de Ciclina p21/genética , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Meia-Vida , Células HeLa , Humanos , Fator 4 Semelhante a Kruppel , Fatores de Transcrição Kruppel-Like/genética , Proteína Supressora de Tumor Von Hippel-Lindau/genética , Proteína Supressora de Tumor Von Hippel-Lindau/metabolismoRESUMO
The function of APC/C (anaphase-promoting complex/cyclosome) was initially implicated with the onset of anaphase during mitosis, where its association with Cdc20 targets securin for destruction, thereby allowing the separation of two duplicated daughter genomes. When combined with Cdh1, APC regulates G1/S transition and DNA replication during cell cycle. Beyond cell cycle control, results from recent biochemical and mouse genetic studies have attracted our attention to the unexpected impact of APC/C(Cdh1) in cellular differentiation, genomic integrity and pathogenesis of various diseases. This review will aim to summarize current understanding of APC/C(Cdh1) in regulating crucial events during development.
Assuntos
Anáfase/fisiologia , Caderinas/metabolismo , Fase G1/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Fase de Repouso do Ciclo Celular/fisiologia , Complexos Ubiquitina-Proteína Ligase/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ciclossomo-Complexo Promotor de Anáfase , Animais , Antígenos CD , Caderinas/genética , Proteínas Cdc20 , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Replicação do DNA , Instabilidade Genômica , Hematopoese/fisiologia , Humanos , Camundongos , Neurogênese/fisiologia , Oogênese/fisiologia , Ligação Proteica , Complexos Ubiquitina-Proteína Ligase/genética , Ubiquitina-Proteína Ligases/genética , UbiquitinaçãoRESUMO
Anaphase-promoting complex/cyclosome (APC/C) is a multifunctional ubiquitin-protein ligase that targets various substrates for proteolysis inside and outside of the cell cycle. The activation of APC/C is dependent on two WD-40 domain proteins, Cdc20 and Cdh1. While APC/Cdc20 principally regulates mitotic progression, APC/Cdh1 shows a broad spectrum of substrates in and beyond cell cycle. In the past several years, numerous biochemical and mouse genetic studies have greatly attracted our attention to the emerging role of APC/Cdh1 in genomic integrity, cellular differentiation and human diseases. This review will aim to summarize the recently expanded understanding of APC/Cdh1 in regulating biological function and how its dysfunction may lead to diseases.
Assuntos
Ciclo Celular/fisiologia , Diferenciação Celular/fisiologia , Genoma , Complexos Ubiquitina-Proteína Ligase/metabolismo , Ciclossomo-Complexo Promotor de Anáfase , Animais , Fase G1/fisiologia , Humanos , Mitose/fisiologia , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patologia , Transdução de Sinais , Complexos Ubiquitina-Proteína Ligase/genéticaRESUMO
HEC1 (highly expressed in cancer), which localizes to kinetochore in cell mitosis, plays an essential role in chromosome segregation for M phase progression. To clarify the mechanism of its transcriptional regulation, we searched out and isolated its 5'-flanking region. Mapping of this region identified that it is a TATA-less promoter and contains several putative binding sites for different transcription factors. The results from HeLa cells transfected with pGL3 luciferase reporter vectors containing progressive deletion of the HEC1 5'-flanking region demonstrated that two elements containing binding sites for cAMP responsive element binding (CREB) protein and activating transcription factor 4 (ATF4 or CREB2) are critical for transcriptional activity. Mutation of the two elements, not downstream E2F box, resulted in a significant reduction of the promoter activity. Gel shift and supershift assays also demonstrated specific binding of transcription factors to their putative binding sites. Furthermore, overexpression of either CREB or ATF4 enhanced the activation of the HEC1 promoter and overexpression of both of them had an additive effect on the activation of the HEC1 transcription. Conversely, overexpression of dominant negative mutants of either CREB or ATF4 resulted in downregulation of HEC1 mRNA significantly. Our study provided a new insight into a potential mechanism of how transcription factors of CREB family are involved in the regulation of kinetochore protein HEC1 in cancer-related cells.
