Metaphase chromosome structure

Gasser, Susan M.; Laroche, Thierry; Falquet, Jacques; Tour, E. Boy de la; Laemmli, Ulrich Karl

doi:10.1016/s0022-2836(86)80010-9

Cited by 500 publications

(115 citation statements)

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“…In agreement with the results reported by Dreyfuss [lo], we find that hnRNP-U/SAF-A is distributed heterogeneously throughout the ndcleus of interphase cells but is excluded from nucleoli (data not shown). In addition, we note that the protein is not present in isolated metaphase chromosomes prepared according to Gasser et al ( [18]; data not shown).…”

Section: Nuclear Localisation Of Hnrnp-uisaf-amentioning

confidence: 55%

Nucleic‐acid‐binding properties of hnRNP‐U/SAF‐A, a nuclear‐matrix protein which binds DNA and RNA in vivo and in vitro

Fackelmayer

Dahm

Renz

et al. 1994

European Journal of Biochemistry

162

147

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We show that SAF-A, a nuclear protein which specifically binds vertebrate scaffold-attachmentregion (SAR) elements with high affinity is identical with hnRNP-U, assumed to be involved in packaging of hnRNA in ribonucleoprotein particles. Ultraviolet cross-linking experiments show that the protein, referred to as hnRNP-U/SAF-A, is bound to chromosomal DNA in vivo. Zn vitro, the isolated protein binds to double-stranded and single-stranded DNA and forms higher ordered nucleic-acid -protein complexes. Filter-binding experiments performed with different types of natural and synthetic nucleic acids as substrates show that the protein binds DNA and RNA with different affinities and most likely at different binding sites. We conclude that hnRNP-U/SAF-A thus may have functions in the organisation of chromosomal DNA in addition to its suggested role in hnRNA metabolism.It is widely believed that DNA in eukaryotic interphase nuclei is organized into loop domains with average lengths of 50-100 kb and that these chromatin loops are bound to internal nuclear structures via the scaffold-attachment region (SAR; for review see [l]) or the matrix-associated region (MAR; for review see 12, 31) DNA elements. Many DNA fragments which specifically bind to internal nuclear structures have been identified, but only little is known about their function in vivo and how they exert this function. In addition, only a few proteins ([4, 51 and references therein) are known which possibly are involved in the binding of these DNA fragments to internal nuclear structures.We have therefore attempted to analyse for nuclear proteins which specifically bind SAR DNA elements and we reported recently on the purification of a DNA binding protein with this property 161. This protein, SAF-A (scaffoldattachment factor A), is a component of the nuclear matrix and of scaffolds; it specifically binds vertebrate SAR DNA elements and reconstitutes looped structures with these DNAs [6]. SAF-A is an abundant protein and the large number of molecules presenthucleus indicate a structural function of this protein. In this communication, we identify SAF-A as hnRNP-U [7], a protein component of heterogeneous nuclear ribonucleoprotein complexes (for review see [S-lo]). We refer to this protein as hnRNP-U/SAF-A and characterize the nucleic-acid binding properties of the protein. We further show by ultraviolet (UV) cross-linking experiments that the protein is bound to DNA in vivo and disCorrespondence to A. Richter,

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Section: Nuclear Localisation Of Hnrnp-uisaf-amentioning

confidence: 55%

Nucleic‐acid‐binding properties of hnRNP‐U/SAF‐A, a nuclear‐matrix protein which binds DNA and RNA in vivo and in vitro

Fackelmayer

Dahm

Renz

et al. 1994

European Journal of Biochemistry

162

147

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“…One of the best characterized components of the chromosomal scaffold is DNA topoisomerase 11 (topo 11) [4][5][6][7]. Besides its enzymatic activity that creates transient double-strand breaks in duplex DNA and passes DNA strands through one another, the protein has been shown to interact with the MAR and SAR elements [8].…”

Section: Introductionmentioning

confidence: 99%

“…255 meres containing highly condensed chromatin, while the lateral loops consist of decondensed, transcriptionally active chromatin covered with numerous nascent transcripts. Because lampbrush chromosome architecture resembles so closely the proposed organization of somatic interphase chromatin and mitotic chromosomes, it is tempting to speculate that the same molecular components might be involved in the maintenance of chromatin loops.One of the best characterized components of the chromosomal scaffold is DNA topoisomerase 11 (topo 11) [4][5][6][7]. Besides its enzymatic activity that creates transient double-strand breaks in duplex DNA and passes DNA strands through one another, the protein has been shown to interact with the MAR and SAR elements [8].…”

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confidence: 99%

DNA Topoisomerase II Is Not Detectable on Lampbrush Chromosomes but Enriched in the Amplified Nucleoli of Xenopus Oocytes

Fischer

Hock

Scheer

1993

Experimental Cell Research

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In somatic cells DNA topoisomerase 11 (topo 11) is thought to be involved in the domain organization of the genome by anchoring the basis of chromatin loops to a chromosomal scaffold. Lampbrush chromosomes of amphibian oocytes directly display this radial loop organization in cytological preparations. In order to find out whether topo 11 may play a role in the organization of these meiotic chromosomes, we performed immunofluorescence studies using antibodies against Xenopus topo 11. Our results indicate that topo 11 is apparently absent from lampbrush chromosomes and is hence unlikely to act as a "fastener" of the numerous lateral chromosomalloops. Topo 11 was, however, enriched in the amplified nucleoli of Xenopus oocytes. © 1993 Academic Press, Inc. INTRODUCTIONThe chromatin fiber of eukaryotic cells is folded into a series of loops or domains which are stabilized by a structural framework called nuclear matrix or chromosomal scaffold. The loops are thought to be anchored at their base to the matrix or scaffold via specific attachment sites, the so-called matrix or scaffold attachment regions (MARs or SARs). Loop length is variable, ranging from 5 to 200 kbp of DNA [for reviews see 1, 2]. Unfortunately, the chromatin loop structures cannot be directly visualized in interphase nuclei with cytological methods because the chromatin strands are highly entangled.The situation is different for amphibian lampbrush chromosomes which can be readily examined under almost native conditions by light microscopy [3]. The structural organization of these meiotic chromosomes exhibits a striking similarity to the loop model described above. Each lampbrush chromosome consists of a chromosomal axis from which numerous loops radiate laterally. The axis represents a linear array of chromo-1 To whom correspondence and reprint requests should be addressed at Zoologie I, Biozentrum Am Hubland, D-97074 Wiirzburg, Germany. Fax: 0049 931 888 4252. 255 meres containing highly condensed chromatin, while the lateral loops consist of decondensed, transcriptionally active chromatin covered with numerous nascent transcripts. Because lampbrush chromosome architecture resembles so closely the proposed organization of somatic interphase chromatin and mitotic chromosomes, it is tempting to speculate that the same molecular components might be involved in the maintenance of chromatin loops.One of the best characterized components of the chromosomal scaffold is DNA topoisomerase 11 (topo 11) [4][5][6][7]. Besides its enzymatic activity that creates transient double-strand breaks in duplex DNA and passes DNA strands through one another, the protein has been shown to interact with the MAR and SAR elements [8]. Thus, topo 11 is thought to have catalytic as well as structural functions. Topo 11 is not only associated with the scaffold of mitotic chromosomes but also the cores and centromeric regions of spermatocyte-derived meiotic chromosomes [9]. Recently Luke and Bogenhagen identified by biochemical means topo 11 in the germinal vesicles of Xenopus o...

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“…This scaffold has been visualized in the electron microscope by histone-depleting chromosomes; the resulting micrographs show Ϸ40-kb DNA loops dangling from a protein-rich aggregate, which is the shape of the original chromosome (3). Isolated scaffolds were shown to contain nonhistone proteins (5) including topoisomerase II (6) and structural maintenance of chromosomes (7). Further studies indicated that the metaphase scaffold is helically folded (8) and contains AT-rich DNA sequences (9,10).…”

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confidence: 99%

Mitotic chromosomes are chromatin networks without a mechanically contiguous protein scaffold

Poirier

Marko

2002

Proc. Natl. Acad. Sci. U.S.A.

159

167

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Isolated newt (Notophthalmus viridescens) chromosomes were studied by using micromechanical force measurement during nuclease digestion. Micrococcal nuclease and short-recognition-sequence blunt-cutting restriction enzymes first remove the native elastic response of, and then to go on to completely disintegrate, single metaphase newt chromosomes. These experiments rule out the possibility that the mitotic chromosome is based on a mechanically contiguous internal non-DNA (e.g., protein) ''scaffold''; instead, the mechanical integrity of the metaphase chromosome is due to chromatin itself. Blunt-cutting restriction enzymes with longer recognition sequences only partially disassemble mitotic chromosomes and indicate that chromatin in metaphase chromosomes is constrained by isolated chromatin-crosslinking elements spaced by Ϸ15 kb.

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Metaphase chromosome structure

Cited by 500 publications

References 50 publications

Nucleic‐acid‐binding properties of hnRNP‐U/SAF‐A, a nuclear‐matrix protein which binds DNA and RNA in vivo and in vitro

Nucleic‐acid‐binding properties of hnRNP‐U/SAF‐A, a nuclear‐matrix protein which binds DNA and RNA in vivo and in vitro

DNA Topoisomerase II Is Not Detectable on Lampbrush Chromosomes but Enriched in the Amplified Nucleoli of Xenopus Oocytes

Mitotic chromosomes are chromatin networks without a mechanically contiguous protein scaffold

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