DNA segregation: Putting chromosomes in their place

Gordon, G. Scott; Wright, Andrew

doi:10.1016/s0960-9822(98)00011-6

Cited by 16 publications

(12 citation statements)

References 13 publications

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“…In contrast to the traditional depiction of the DNA replication fork moving along DNA, the replisome remains relatively stable in the cell, while new copies of the chromosome are extruded from it and pass toward opposite poles (Gordon and Wright 1998). Similarly, instead of strand exchange simply increasing the size of the D-loop of two closely adjoined recombination partners, increasing the compaction and stability of joint molecules through the reestablishment of chromatin could be a (CSHJ).…”

Section: Resultsmentioning

confidence: 99%

Analysis of Close Stable Homolog Juxtaposition During Meiosis in Mutants ofSaccharomyces cerevisiae

Lui¹,

Peoples-Holst²,

et al. 2006

Genetics

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A unique aspect of meiosis is the segregation of homologous chromosomes at the meiosis I division. The pairing of homologous chromosomes is a critical aspect of meiotic prophase I that aids proper disjunction at anaphase I. We have used a site-specific recombination assay in Saccharomyces cerevisiae to examine allelic interaction levels during meiosis in a series of mutants defective in recombination, chromatin structure, or intracellular movement. Red1, a component of the chromosome axis, and Mnd1, a chromosome-binding protein that facilitates interhomolog interaction, are critical for achieving high levels of allelic interaction. Homologous recombination factors (Sae2, Rdh54, Rad54, Rad55, Rad51, Sgs1) aid in varying degrees in promoting allelic interactions, while the Srs2 helicase appears to play no appreciable role. Ris1 (a SWI2/ SNF2 related protein) and Dot1 (a histone methyltransferase) appear to play minor roles. Surprisingly, factors involved in microtubule-mediated intracellular movement (Tub3, Dhc1, and Mlp2) appear to play no appreciable role in homolog juxtaposition, unlike their counterparts in fission yeast. Taken together, these results support the notion that meiotic recombination plays a major role in the high levels of homolog interaction observed during budding yeast meiosis.M EIOSIS is the process by which a parent diploid cell undergoes one round of DNA replication followed by two rounds of chromosome segregation to yield haploid gametes. A unique aspect of meiosis is the segregation of homologous chromosomes at the first meiotic division. Nondisjunction, or improper segregation of homologs, at this stage can lead to gamete aneuploidy, which is a major cause of birth defects in humans (Hassold and Hunt 2001). Homologs are able to correctly orient toward opposite poles of the meiosis I spindle, because a collaboration of DNA crossovers (CR) with sister-chromatid cohesion forms temporary connections between the homologs (Page and Hawley 2003;Petronczki et al. 2003).Homologous chromosomes form progressively stronger associations as cells proceed through meiotic prophase I (Zickler and Kleckner 1999;Storlazzi et al. 2003). In the budding yeast, plants, and mammals, transacting factors required for meiotic recombination are crucial for the pairing and crossing over between homologous chromosomes. In contrast, synaptonemal complex (SC) formation, meiotic nuclear reorganization, and an achiasmate segregation system appear to play supplementary roles in meiotic homolog pairing in the budding yeast (Loidl et al.

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Section: Resultsmentioning

confidence: 99%

Analysis of Close Stable Homolog Juxtaposition During Meiosis in Mutants ofSaccharomyces cerevisiae

Lui¹,

Peoples-Holst²,

et al. 2006

Genetics

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“…The positions of the replication forks can be predicted by the Factory Model of replication (Gordon and Wright, 1998; Lemon and Grossman, 1998). The machinery for DNA replication in slow growing cells is fixed at the cell center.…”

Section: Discussionmentioning

confidence: 99%

A case for sliding SeqA tracts at anchored replication forks during Escherichia coli chromosome replication and segregation

et al. 2000

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SeqA is an Escherichia coli DNA‐binding protein that acts at replication origins and controls DNA replication. However, binding is not exclusive to origins. Many fragments containing two or more hemi‐methylated GATC sequences bind efficiently. Binding was optimal when two such sequences were closely apposed or up to 31 bases apart on the same face of the DNA helix. Binding studies suggest that neighboring bound proteins contact each other to form a complex with the intervening DNA looped out. There are many potential binding sites distributed around the E.coli chromosome. As replication produces a transient wave of hemi‐methylation, tracts of SeqA binding are likely to associate with each fork as replication progresses. The number and positions of green fluorescent protein–SeqA foci seen in living cells suggest that they correspond to these tracts, and that the forks are tethered to planes of cell division. SeqA may help to tether the forks or to organize newly replicated DNA into a structure that aids DNA to segregate away from the replication machinery.

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“…The DNA replication process itself drives DNA segregation, pushing the newly replicated DNA outward from the anchored replication forks towards opposite cell poles. This results in two substantially separated nucleoid masses on termination of replication (Gordon and Wright, 1998; Lemon and Grossman, 1998). Figure 1 assumes that newly replicated DNA is added to the inside border of the nascent nucleoid.…”

Section: The Factory Model For Dna Replication and Segregationmentioning

confidence: 99%

An analysis of the factory model for chromosome replication and segregation in bacteria

Sawitzke

Austin²

2001

Molecular Microbiology

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Recent advances in microscopy have given us important clues as to the nature of chromosome segregation in bacteria. Most current observations favour the view that the process is co‐replicational: DNA replication forks are anchored at the cell centre, and the newly replicated DNA is moved towards the cell poles. This scheme can account for orderly segregation even at high growth rates where multiple replication cycles overlap. We argue that there are five distinct activities directly involved in co‐replicational segregation dynamics. These we refer to as Push, Direct, Condense, Hold and Clear. We attempt to assign one of these roles to each protein implicated in chromosome segregation. The proposed process is very different from mitosis in eukaryotic cells and perhaps more closely resembles the formation of separate sister chromatids during DNA replication.

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DNA segregation: Putting chromosomes in their place

Cited by 16 publications

References 13 publications

Analysis of Close Stable Homolog Juxtaposition During Meiosis in Mutants ofSaccharomyces cerevisiae

Analysis of Close Stable Homolog Juxtaposition During Meiosis in Mutants ofSaccharomyces cerevisiae

A case for sliding SeqA tracts at anchored replication forks during Escherichia coli chromosome replication and segregation

An analysis of the factory model for chromosome replication and segregation in bacteria

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