The kelch protein NS1-BP interacts with alpha-enolase/MBP-1 and is involved in c-Myc gene transcriptional control.
Alpha-enolase is a key glycolytic enzyme that plays a functional role in several physiological processes depending on the cellular localization. The enzyme is mainly localized in the cytoplasm whereas an alternative translated form, named MBP-1, is predominantly nuclear. The MBP-1 protein has been characterized as a c-Myc promoter binding protein that negatively controls transcription. In the present study, we identified the kelch protein NS1-BP as one of the alpha-enolase/MBP-1 partners by using a yeast two-hybrid screening. Although NS1-BP has been originally described as a protein mainly localized in the nucleus, we provide evidence that NS1-BP also interacts with actin in human cells, as reported for most kelch-containing proteins. Here we showed that alpha-enolase and MBP-1 associate with NS1-BP in vitro and in vivo by GST pull-down assays and coimmunoprecipitation experiments; subsequent immunofluorescent staining confirmed colocalization of the proteins within the cells. Furthermore, functional analyses performed by cotransfection assays revealed that NS1-BP enhances the inhibitory effect exerted by MBP-1 on c-Myc promoter. In mammalian cells, the overexpression of both proteins resulted in an increased repression of basal c-Myc transcription and consistently affected the steady state levels of endogenous c-Myc mRNA. These findings further support the distinct roles of alpha-enolase and its MBP-1 variant in maintaining cell homeostasis. Moreover, our data suggest a novel function for NS1-BP in the control of cell proliferation.
Perconti
Giovanni
G
Dipartimento di Oncologia Sperimentale e Applicazioni Cliniche, Università di Palermo, Italy.
Ferro
Arianna
A
Amato
Felice
F
Rubino
Patrizia
P
Randazzo
Davide
D
Wolff
Thorsten
T
Feo
Salvatore
S
Giallongo
Agata
A
D000199:Actins / Q000378:metabolism; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D021381:Protein Transport; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D016601:RNA-Binding Proteins; D013347:Subcellular Fractions; D014157:Transcription Factors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D000199:Actins; D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C114207:IVNS1ABP protein, human; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C095157:ENO1 protein, human; D010751:Phosphopyruvate Hydratase