title: Identification of a novel "chromosome scaffold" protein that associates with Tec elements undergoing en masse elimination in Euplotes crassus.
abstract: During macronuclear development in the ciliate Euplotes crassus, the highly repetitive, transposon-like Tec elements possess an unusual chromatin structure. We observed that the Tec element chromatin is highly resistant to salt extraction and behaves like a nuclear matrix/chromosome scaffold-associated structure. Standard matrix/scaffold extraction procedures identified two major proteins: 1) an ~140-kDa protein that seems to be topoisomerase II based on its reactivity with anti-topoisomerase II antibodies, and 2) an 85-kDa protein that we further purified by acid extraction and have shown to be a novel protein by sequence analysis of its gene. The 85-kDa protein (p85) is a developmental stage-specific protein and is located exclusively in the developing macronucleus. Immunolocalization studies of p85 show that it colocalizes with topoisomerase II in chromatin. In addition, in situ hybridization combined with immunofluorescence localization of the proteins indicates that 100% of the Tec elements colocalize with 70% of the p85, whereas no significant colocalization with a total macronuclear sequence-specific probe is observed. p85 is the first developmental stage-specific protein identified as being specifically associated with sequences undergoing elimination in E. crassus.
authors.affiliation: Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60611-3008, USA.
authors.forename: Suzanne I
authors.initials: SI
authors.lastname: Sharp
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Pickrell
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Jahn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004251:DNA Transposable Elements; D004305:Dose-Response Relationship, Drug; D016812:Euplotes / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D017403:In Situ Hybridization; D008856:Microscopy, Fluorescence; D008938:Mitosis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D002843:Chromatin; D004251:DNA Transposable Elements; D006657:Histones; D009687:Nuclear Proteins; D012965:Sodium Chloride; D004250:DNA Topoisomerases, Type II