MXD1 localizes in the nucleolus, binds UBF and impairs rRNA synthesis

Maria del Carmen Lafita-Navarro, Rosa Blanco, Jorge Mata-Garrido, Judit Liaño-Pons, Olga Tapia, Lucía García-Gutiérrez, Eva García-Alegría, María T. Berciano, Miguel Lafarga, Javier León

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

MXD1 is a protein that interacts with MAX, to form a repressive transcription factor. MXD1-MAX binds E-boxes. MXD1-MAX antagonizes the transcriptional activity of the MYC oncoprotein in most models. It has been reported that MYC overexpression leads to augmented RNA synthesis and ribosome biogenesis, which is a relevant activity in MYC-mediated tumorigenesis. Here we describe that MXD1, but not MYC or MNT, localizes to the nucleolus in a wide array of cell lines derived from different tissues (carcinoma, leukemia) as well as in embryonic stem cells. MXD1 also localizes in the nucleolus of primary tissue cells as neurons and Sertoli cells. The nucleolar localization of MXD1 was confirmed by co-localization with UBF. Co-immunoprecipitation experiments showed that MXD1 interacted with UBF and proximity ligase assays revealed that this interaction takes place in the nucleolus. Furthermore, chromatin immunoprecipitation assays showed that MXD1 was bound in the transcribed rDNA chromatin, where it co-localizes with UBF, but also in the ribosomal intergenic regions. The MXD1 involvement in rRNA synthesis was also suggested by the nucleolar segregation upon rRNA synthesis inhibition by actinomycin D. Silencing of MXD1 with siRNAs resulted in increased synthesis of pre-rRNA while enforced MXD1 expression reduces it. The results suggest a new role for MXD1, which is the control of ribosome biogenesis. This new MXD1 function would be important to curb MYC activity in tumor cells.

Original languageEnglish (US)
Pages (from-to)69536-69548
Number of pages13
JournalOncotarget
Volume7
Issue number43
DOIs
StatePublished - 2016

Keywords

  • MXD1
  • Nucleolus
  • Pre-rRNA
  • Transcription regulation
  • UBF

ASJC Scopus subject areas

  • Oncology

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