scholarly journals Functional aspects of the nuclear matrix.

1995 ◽  
Vol 42 (2) ◽  
pp. 127-131 ◽  
Author(s):  
F Wanka
Keyword(s):  
Dna Sequences ◽  
Nuclear Matrix ◽  
Specific Protein ◽  
Dna Unwinding ◽  
Replication Origins ◽  
Repeated Dna ◽  
Chromosomal Dna ◽  
Double Stranded Dna ◽  
Functional Aspects ◽  
The Matrix

A model is proposed of the way in which the unwinding of the chromosomal DNA loops is controlled during DNA replication. It is based on the observation of a permanent binding of replication origins to the nuclear matrix and of a transient attachment of replicating DNA regions to sites in the immediate neighbourhood. DNA unwinding is controlled while the replicating loops are reeled through the replication binding sites. Also a mechanism is proposed to explain how the once-per-cycle replication of individual replicons can be controlled. DNA synthesis is initiated at single-stranded loops exposed by tandemly repeated DNA sequences at the replication origins. The single-stranded loops turn into fully double-stranded DNA during replication, becoming inaccessible for a second initiation during the same cell cycle. The configuration competent for initiation is restored by specific protein-DNA rearrangements coupled to mitotic condensation of the matrix into chromosomal scaffolds and its reversal.

scholarly journals Replication of G Quadruplex DNA

Genes ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 95 ◽  
Author(s):  
Leticia Koch Lerner ◽  
Julian E. Sale
Keyword(s):  
Dna Replication ◽  
Dna Sequences ◽  
Secondary Structures ◽  
Dna Unwinding ◽  
Chromosomal Dna ◽  
Quadruplex Dna ◽  
Epigenetic Instability ◽  
G Quadruplex ◽  
Dna Secondary Structures ◽  
Dna Template

A cursory look at any textbook image of DNA replication might suggest that the complex machine that is the replisome runs smoothly along the chromosomal DNA. However, many DNA sequences can adopt non-B form secondary structures and these have the potential to impede progression of the replisome. A picture is emerging in which the maintenance of processive DNA replication requires the action of a significant number of additional proteins beyond the core replisome to resolve secondary structures in the DNA template. By ensuring that DNA synthesis remains closely coupled to DNA unwinding by the replicative helicase, these factors prevent impediments to the replisome from causing genetic and epigenetic instability. This review considers the circumstances in which DNA forms secondary structures, the potential responses of the eukaryotic replisome to these impediments in the light of recent advances in our understanding of its structure and operation and the mechanisms cells deploy to remove secondary structure from the DNA. To illustrate the principles involved, we focus on one of the best understood DNA secondary structures, G quadruplexes (G4s), and on the helicases that promote their resolution.

scholarly journals INDUCTION OF INTRACHROMOSOMAL RECOMBINATION IN YEAST BY INHIBITION OF THYMIDYLATE BIOSYNTHESIS

Genetics ◽  
1986 ◽  
Vol 114 (2) ◽  
pp. 375-392
Author(s):  
B A Kunz ◽  
G R Taylor ◽  
R H Haynes
Keyword(s):  
Gene Conversion ◽  
Dna Sequences ◽  
Dna Hybridization ◽  
Crossing Over ◽  
Repeated Dna ◽  
Yeast Saccharomyces Cerevisiae ◽  
Haploid Strain ◽  
Reciprocal Exchange ◽  
Coli Plasmid ◽  
Antifolate Drugs

ABSTRACT The biosynthesis of thymidylate in the yeast Saccharomyces cerevisiae can be inhibited by antifolate drugs. We have found that antifolate treatment enhances the formation of leucine prototrophs in a haploid strain of yeast carrying, on the same chromosome, two different mutant leu2 alleles separated by Escherichia coli plasmid sequences. That this effect is a consequence of thymine nucleotide depletion was verified by the finding that provision of exogenous thymidylate eliminates the increased production of Leu+ colonies. DNA hybridization analysis revealed that recombination, including reciprocal exchange, gene conversion and unequal sister-chromatid crossing over, between the duplicated genes gave rise to the induced Leu+ segregants. Although gene conversion unaccompanied by crossing over was responsible for the major fraction of leucine prototrophs, events involving reciprocal exchange exhibited the largest increase in frequency. These data show that recombination is induced between directly repeated DNA sequences under conditions of thymine nucleotide depletion. In addition, the results of this and previous studies are consistent with the possibility that inhibition of thymidylate biosynthesis in yeast may create a metabolic condition that provokes all forms of mitotic recombination.

Highly repeated DNA sequences in birds: The structure and evolution of an abundant, tandemly repeated 190-bp DNA fragment in parrots

Genomics ◽  
1992 ◽  
Vol 14 (2) ◽  
pp. 462-469 ◽  
Author(s):  
Cort S. Madsen ◽  
Dineke H. de Kloet ◽  
Jean E. Brooks ◽  
Siwo R. de Kloet
Keyword(s):  
Dna Sequences ◽  
Repeated Dna ◽  
Repeated Dna Sequences ◽  
Highly Repeated Dna ◽  
Dna Fragment
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