title: HAC stability in murine cells is influenced by nuclear localization and chromatin organization.
abstract: BACKGROUND
  Human artificial chromosomes (HAC) are small functional extrachromosomal elements, which segregate correctly during each cell division. In human cells, they are mitotically stable, however when the HAC are transferred to murine cells they show an increased and variable rate of loss. In some cell lines the HAC are lost over a short period of time, while in others the HAC become stable without acquiring murine DNA.
  
  
  RESULTS
  In this study, we linked the loss rate to the position of the HAC in the murine cell nucleus with respect to the chromocenters. HAC that associated preferentially with the chromocenter displayed a lower loss rate compared to the HAC that are less frequently associated. The chromocenter acts as a hub for the deposition of heterochromatic markers, controlling centromeric and pericentromeric DNA replication timing and chromosome segregation. The HAC which localized more frequently outside the chromocenters bound variable amounts of histone H3 tri-methylated at lysine 9, and the high level of intraclonal variability was associated with an increase in HAC segregation errors and delayed DNA replication timing.
  
  
  CONCLUSIONS
  This is a novel result indicating that HAC segregation is closely linked to the position in the murine nucleus and gives important insight for HAC gene expression studies in murine cells and establishing murine models of human genetic disease.
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK. dmoralli@well.ox.ac.uk
authors.forename: Daniela
authors.initials: D
authors.lastname: Moralli
authors.forename: David Y L
authors.initials: DY
authors.lastname: Chan
authors.forename: Andrew
authors.initials: A
authors.lastname: Jefferson
authors.forename: Emanuela V
authors.initials: EV
authors.lastname: Volpi
authors.forename: Zoia L
authors.initials: ZL
authors.lastname: Monaco
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics; D002503:Centromere / Q000502:physiology; D002843:Chromatin / Q000737:chemistry* / Q000378:metabolism; D043171:Chromosomal Instability; D022222:Chromosomes, Artificial, Human / Q000235:genetics* / Q000378:metabolism*; D018014:Gene Transfer Techniques; D006657:Histones / Q000378:metabolism; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008677:Metaphase; D051379:Mice; D008938:Mitosis
chemical_list: D002843:Chromatin; D006657:Histones