Localization of phosphorylated forms of Bcl-2 in mitosis: co-localization with Ki-67 and nucleolin in nuclear structures and on mitotic chromosomes.
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.
Barboule
Nadia
N
Laboratoire de Biologie Cellulaire et Moléculaire du Contrôle de la Prolifération, Université Paul Sabatier, Toulouse cédex, France. barboule@cict.fr
Truchet
Isabelle
I
Valette
Annie
A
D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D002875:Chromosomes / Q000648:ultrastructure; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D019394:Ki-67 Antigen / Q000096:biosynthesis*; D008856:Microscopy, Fluorescence; D008938:Mitosis; D010750:Phosphoproteins / Q000096:biosynthesis*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000096:biosynthesis*; D013347:Subcellular Fractions / Q000737:chemistry; D000097796:Nucleolin
D019394:Ki-67 Antigen; D010750:Phosphoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016601:RNA-Binding Proteins; D000097796:Nucleolin