Pontin is a multifunctional protein having roles in various cellular processes including regulation of gene expression. Here, we addressed Pontin intracellular localization using two different monoclonal antibodies directed against different Pontin epitopes. For the first time, Pontin was directly visualized in nucleoli where it co-localizes with Upstream Binding Factor and RNA polymerase I. Nucleolar localization of Pontin was confirmed by its detection in nucleolar extracts and by electron microscopy, which revealed Pontin accumulation specifically in the nucleolar fibrillar centers. Pontin localization in the nucleolus was dynamic and Pontin accumulated in large nucleolar dots mainly during S-phase. Pontin concentration in the large nucleolar dots correlated with reduced transcriptional activity of nucleoli. In addition, Pontin was found to associate with RNA polymerase I and to interact in a complex with c-Myc with rDNA sequences indicating that Pontin is involved in the c-Myc-dependent regulation of rRNA synthesis.

• MeSH
• ATPases Associated with Diverse Cellular Activities MeSH
• Cell Nucleolus enzymology   ultrastructure   MeSH
• DNA Helicases metabolism   MeSH
• Transcription, Genetic MeSH
• HeLa Cells MeSH
• Humans MeSH
• RNA, Ribosomal biosynthesis   MeSH
• RNA Polymerase I metabolism   MeSH
• Pol1 Transcription Initiation Complex Proteins metabolism   MeSH
• Microscopy, Electron, Transmission MeSH
• Carrier Proteins metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• ATPases Associated with Diverse Cellular Activities MeSH
• DNA Helicases MeSH
• RNA, Ribosomal MeSH
• RNA Polymerase I MeSH
• RUVBL1 protein, human MeSH Browser
• transcription factor UBF MeSH Browser
• Pol1 Transcription Initiation Complex Proteins MeSH
• Carrier Proteins MeSH