Localization of phosphorylated forms of Bcl-2 in mitosis: co-localization with Ki-67 and nucleolin in nuclear structures and on mitotic chromosomes

Cell Cycle. 2005 Apr;4(4):590-6. doi: 10.4161/cc.4.4.1588. Epub 2005 Apr 18.

Abstract

Bcl-2 phosphorylation is a normal physiological process occurring at mitosis or during mitotic arrest induced by microtubule damaging agents. The consequences of Bcl-2 phosphorylation on its function are still controversial. To better understand the role of Bcl-2 phosphorylation in mitosis, we studied the subcellular localization of phosphorylated forms of Bcl-2. Immunofluorescence experiments performed in synchronized HeLa cells indicate for the first time that mitotic phosphorylated forms of Bcl-2 can be detected in nuclear structures in prophase cells together with nucleolin and Ki-67. In later mitotic stages, as previously described, phosphorylated forms of Bcl-2 are localized on mitotic chromosomes. In addition, we demonstrate that Bcl-2 in these structures is at least in part phosphorylated on the T56 residue. Then, coimmunoprecipitation experiments reveal that, in cells synchronized at the onset of mitosis, Bcl-2 is present in a complex with nucleolin, cdc2 kinase and PP1 phosphatase. Taken together, these data further support the idea that Bcl-2 could have a new function at mitosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle
  • Cell Nucleus / metabolism
  • Chromosomes / ultrastructure
  • Gene Expression Regulation, Neoplastic*
  • HeLa Cells
  • Humans
  • Immunoprecipitation
  • Ki-67 Antigen / biosynthesis*
  • Microscopy, Fluorescence
  • Mitosis
  • Nucleolin
  • Phosphoproteins / biosynthesis*
  • Phosphorylation
  • Proto-Oncogene Proteins c-bcl-2 / chemistry*
  • Proto-Oncogene Proteins c-bcl-2 / physiology*
  • RNA-Binding Proteins / biosynthesis*
  • Subcellular Fractions / chemistry

Substances

  • Ki-67 Antigen
  • Phosphoproteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA-Binding Proteins