title: Large-scale organization of ribosomal DNA chromatin is regulated by Tip5.
abstract: The DNase I accessibility and chromatin organization of genes within the nucleus do correlate to their transcriptional activity. Here, we show that both serum starvation and overexpression of Tip5, a key regulator of ribosomal RNA gene (rDNA) repression, dictate DNase I accessibility, facilitate the association of rDNA with the nuclear matrix and thus regulate large-scale rDNA chromatin organization. Tip5 contains four AT-hooks and a TAM (Tip5/ARBP/MBD) domain, which were proposed to bind matrix-attachment regions (MARs) of the genome. Remarkably, the TAM domain of Tip5 functions as nucleolar localization and nuclear matrix targeting module, whereas AT-hooks do not mediate association with the nuclear matrix, but they are required for nucleolar targeting. These findings suggest a dual role for Tip5's AT-hooks and TAM domain, targeting the nucleolus and anchoring to the nuclear matrix, and suggest a function for Tip5 in the regulation of higher-order rDNA chromatin structure.
authors.affiliation: Department of Biochemistry III, Biochemistry Center Regensburg, University of Regensburg, Universitätsstr 31, D-93053 Regensburg, Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Zillner
authors.forename: Michael
authors.initials: M
authors.lastname: Filarsky
authors.forename: Katrin
authors.initials: K
authors.lastname: Rachow
authors.forename: Michael
authors.initials: M
authors.lastname: Weinberger
authors.forename: Gernot
authors.initials: G
authors.lastname: Längst
authors.forename: Attila
authors.initials: A
authors.lastname: Németh
mesh_terms: D001692:Biological Transport; D002460:Cell Line; D002466:Cell Nucleolus / Q000648:ultrastructure; D002843:Chromatin / Q000737:chemistry*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D045170:Matrix Attachment Regions; D015530:Nuclear Matrix / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000092468:Bromodomain Containing Proteins
chemical_list: D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004275:DNA, Ribosomal; C436708:BAZ2A protein, human; D000092468:Bromodomain Containing Proteins