title: Cell cycle-dependent 3D distribution of telomeres and telomere repeat-binding factor 2 (TRF2) in HaCaT and HaCaT-myc cells.
abstract: Telomeres are specialized structures at the ends of the chromosomes that, with the help of proteins--such as the telomere repeat-binding factor TRF2 -, form protective caps which are essential for chromosomal integrity. Investigating the structure and three-dimensional (3D) distribution of the telomeres and TRF2 in the nucleus, we now show that the telomeres of the immortal HaCaT keratinocytes are distributed in distinct non-overlapping territories within the inner third of the nuclear space in interphase cells, while they extend more widely during mitosis. TRF2 is present at the telomeres at all cell cycle phases. During mitosis additional TRF2 protein concentrates all around the chromosomes. This change in staining pattern correlates with a significant increase in TRF2 protein at the S/G2 transition as seen in Western blots of synchronized cells and is paralleled by a cell cycle-dependent regulation of TRF2 mRNA, arguing for a specific role of TRF2 during mitosis. The distinct territorial localization of telomeres is abrogated in a HaCaT variant that constitutively expresses c-Myc--a protein known to contribute to genomic instability. These cells are characterized by overlapping telomere territories, telomeric aggregates (TAs), that are accompanied by an overall irregular telomere distribution and a reduced level in TRF2 protein. These TAs which are readily detectable in interphase nuclei, are similarly present in mitotic cells, including cells in telophase. Thus, we propose that TAs, which subsequently also cluster their respective chromosomes, contribute to genomic instability by forcing an abnormal chromosome segregation during mitosis.
authors.affiliation: German Cancer Research Center, Heidelberg, Germany.
authors.forename: Sibylle
authors.initials: S
authors.lastname: Ermler
authors.forename: Damir
authors.initials: D
authors.lastname: Krunic
authors.forename: Tobias A
authors.initials: TA
authors.lastname: Knoch
authors.forename: Sharareh
authors.initials: S
authors.lastname: Moshir
authors.forename: Sabine
authors.initials: S
authors.lastname: Mai
authors.forename: Karin M
authors.initials: KM
authors.lastname: Greulich-Bode
authors.forename: Petra
authors.initials: P
authors.lastname: Boukamp
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D002877:Chromosomes, Human / Q000378:metabolism; D042822:Genomic Instability / Q000502:physiology*; D006801:Humans; D008938:Mitosis / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism / Q000502:physiology; D016615:Telomere / Q000737:chemistry / Q000378:metabolism*; D035341:Telomeric Repeat Binding Protein 2 / Q000032:analysis / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D035341:Telomeric Repeat Binding Protein 2