title: Evidence showing that the nucleolus-envelope region is located on the nor-bearing chromosomes in Aotus trivirgatus.
abstract: We investigated whether the existence of the Nucleolus-Envelope Region observed in dividing animal cells is related to the Nucleolus Organizer Region or to other chromosome segments of the NOR-bearing chromosomes, since NORs are usually adjacent to the chromosome segments attached to the nuclear envelope such as the centromere, telomere or heterochromatin region. We used Aotus Trivirgatus fibroblasts whose karyotype is characterized by a single pair of NORs located on the long arm of the third pair of chromosomes, far from the centromere, the telomere and any obvious heterochromatin region. All the nucleoli were seen to be clearly associated with the nuclear envelope but separated from it by the outermost layer of chromatin. These results further support the hypothesis that the NOR is a site of attachment of the chromatin to the nuclear envelope by means of the Nucleolus-Envelope Region. They show that genetically active chromatin is also attached to the nuclear envelope. A model of the arrangement of chromatin during interphase is proposed which provides a functional interpretation of the currently available data.
mesh_terms: D000818:Animals; D001029:Aotus trivirgatus; D002466:Cell Nucleolus / Q000648:ultrastructure*; D002843:Chromatin / Q000378:metabolism; D002875:Chromosomes / Q000648:ultrastructure*; D004247:DNA / Q000378:metabolism; D005347:Fibroblasts / Q000648:ultrastructure; D007399:Interphase
chemical_list: D002843:Chromatin; D004247:DNA