title: Lampbrush chromosomes enable study of cohesin dynamics.
abstract: The lampbrush chromosomes present in the nuclei of amphibian oocytes offer unique biological approaches for study of the mechanisms that regulate chromatin structure with high spatial resolution. We discuss fundamental aspects of the remarkable organization and plasticity exhibited by lampbrush chromosomes. We then utilize lampbrush chromosomes to characterize the chromosomal distribution and dynamics of cohesin, the four-protein complex (RAD21/MCD1/SCC1, SMC1, SMC3, SCC3/SA2) responsible for sister chromatid cohesion. We find that endogenous SMC3 and newly expressed hRAD21 co-localize on chromosomal axes, sites where sister chromatids are tightly paired. We present evidence suggesting that hRAD21 recruitment to lampbrush chromosomes is modulated by chromosomal SMC1 and SMC3. Notably, using a technique for de novo chromosome assembly, we demonstrate that both SMC3 and hRAD21 are recruited to single, unreplicated lampbrush chromatids. Finally, we used our novel method of analyzing the oocyte nucleus under oil combined with fluorescence recovery after photobleaching, to provide direct evidence that cohesin is highly dynamic at discrete, condensed chromosomal regions. Collectively, these data demonstrate that lampbrush chromosomes provide a unique and powerful tool for combining biochemical and cytological analyses for dissection of complex chromosomal processes.
authors.affiliation: Cell & Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Austin
authors.forename: Natalya
authors.initials: N
authors.lastname: Novikova
authors.forename: Vincent
authors.initials: V
authors.lastname: Guacci
authors.forename: Michel
authors.initials: M
authors.lastname: Bellini
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology*; D002467:Cell Nucleus / Q000648:ultrastructure; D002842:Chromatids / Q000378:metabolism / Q000648:ultrastructure; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis / Q000378:metabolism* / Q000502:physiology*; D002875:Chromosomes / Q000378:metabolism* / Q000648:ultrastructure; D004268:DNA-Binding Proteins; D005260:Female; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D008858:Microscopy, Phase-Contrast; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D009865:Oocytes / Q000648:ultrastructure; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D025941:Protein Interaction Mapping; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000502:physiology; D029867:Xenopus Proteins / Q000032:analysis / Q000502:physiology*; D014982:Xenopus laevis; D000097722:Cohesins; D000098550:Structural Maintenance of Chromosome Protein 1
chemical_list: D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; D000097722:Cohesins; D000098550:Structural Maintenance of Chromosome Protein 1; C429022:RAD21 protein, human; C490528:Rad21 protein, Xenopus; C541513:SCC3 protein, Xenopus; C541512:SMC3 protein, Xenopus