Aspects of Tandemly Organized, Repetitive Sequences in Chromosomal DNA

2002 ◽  
pp. 1-10 ◽  
Author(s):  
J. T. Epplen ◽  
A. Epplen-Haupt
Keyword(s):  
Repetitive Sequences ◽  
Chromosomal Dna

scholarly journals The Mechanism of Replication Stalling and Recovery within Repetitive DNA

2021 ◽  
Author(s):  
Corella S Casas-Delucchi ◽  
Manuel Daza-Martin ◽  
Sophie L Williams ◽  
Gideon Coster
Keyword(s):  
Cellular Response ◽  
Repetitive Sequences ◽  
Replication Stress ◽  
Underlying Mechanism ◽  
Dna Lesions ◽  
Chromosomal Dna ◽  
Leading Strand ◽  
Fork Stalling ◽  
Dna Template

SUMMARYAccurate chromosomal DNA replication is essential to maintain genomic stability. Genetic evidence suggests that certain repetitive sequences impair replication, yet the underlying mechanism is poorly defined. Replication could be directly inhibited by the DNA template or indirectly, for example by DNA-bound proteins. Here, we reconstituted replication of mono-, di- and trinucleotide repeats in vitro using eukaryotic replisomes assembled from purified proteins. We found that structure-prone repeats are sufficient to impair replication. Whilst template unwinding was unaffected, leading strand synthesis was inhibited, leading to fork uncoupling. Synthesis through hairpin-forming repeats relied on replisome-intrinsic mechanisms, whereas synthesis of quadruplex-forming repeats required an extrinsic accessory helicase. DNA-induced fork stalling was mechanistically similar to that induced by leading strand DNA lesions, highlighting structure-prone repeats as an important potential source of replication stress. Thus, we propose that our understanding of the cellular response to replication stress also applies to stalling induced by repetitive sequences.

The organization of transcription on lampbrush chromosomes

1978 ◽  
Vol 283 (997) ◽  
pp. 359-366 ◽  
Keyword(s):  
Messenger Rna ◽  
Repetitive Sequences ◽  
Simple Explanation ◽  
Lampbrush Chromosomes ◽  
Chromosomal Dna ◽  
Rna Sequences ◽  
Nonhistone Proteins ◽  
Rna Transcripts ◽  
Biochemical Studies ◽  
Regular Arrays

The meiotic lampbrush chromosomes of amphibian oocytes display readily distinguishable regions of transcription (lateral loops) which extend from axial condensates of chromatin (chromomeres). The chromomeres contain most of the chromosomal DNA which, along with histone, is tightly compacted as regular arrays of DNP. Many RNA transcripts are generated on the lateral loops, and heterogeneous nonhistone proteins associate with these transcripts, forming periodic condensates of 20-30 nm ribonucleoprotein (RNP) particles. These unit particles aggregate in various ways and to varying degrees and thereby confer distinctive gross morphologies to particular loops. There are about 10 4 lateral loops per haploid complement of newt chromosomes and this figure is similar to the experimentally derived number of different messenger RNA sequences found in oocytes. From cytological and biochemical studies it is now possible to consider individual lateral loops from various aspects: as morphologically distinct units; as units of inheritance; as units of functional activity; as units of transcription; as units of transcribed repetitive sequences; and as units containing one coding sequence. The difficulties in arriving at a simple explanation of the organization of transcription in lampbrush chromosomes are discussed.

Chromosomal DNA in higher plants

1981 ◽  
Vol 292 (1062) ◽  
pp. 569-578 ◽  
Keyword(s):  
Repetitive Dna ◽  
Functional Significance ◽  
Higher Plants ◽  
Repetitive Sequences ◽  
Chromosomal Dna ◽  
Dna Amount ◽  
Cell Divisions ◽  
Specific Effects ◽  
Base Sequences ◽  
Per Se

There is an astonishing variation in the amount of chromosomal DNA among species of higher plants. Much of this variation is due to the amplification of base sequences within the chromosomes. As a result, the amount of DNA in the nuclei of many species is very great. In particular, the chromosomes are rich in repetitive DNA, which may comprise 70 % or more of the total. This fraction contains at most only a few genes that code for proteins. What, then, is its functional significance? There is evidence that DNA amount per se affects cell size and the duration of cell divisions. The results of recent assays also provide evidence that particular repetitive sequences have specific effects upon the phenotype. While these effects may be small in themselves they may nevertheless be important in Nature and in plant breeding

Isolation and partial characterization of plasmids found in three Halobacterium volcanii isolates

1989 ◽  
Vol 35 (1) ◽  
pp. 92-95 ◽  
Author(s):  
Ilan Rosenshine ◽  
Moshe Mevarech
Keyword(s):  
Key Words ◽  
Protoplast Fusion ◽  
Repetitive Sequences ◽  
Partial Characterization ◽  
Restriction Maps ◽  
Chromosomal Dna ◽  
Fusion Technique ◽  
Homologous Sequences ◽  
Halobacterium Volcanii

Three new isolates of Halobacterium volcanii were screened for the presence of plasmids. Each of the different isolates was found to contain one plasmid. These plasmids do not show any homology to each other, nor to the previously isolated plasmid pHV2. Partial restriction maps of these plasmids were determined. One of the plasmids contains chromosomal repetitive sequences as judged by the existence of homologous sequences in the chromosomal DNA of the three isolates. Using the protoplast fusion technique, we showed that at least one of the newly isolated plasmids is compatible with pHV2.Key words: Halobacterium volcanii, archaebacterium, plasmids.

Active maize genes are unmodified and flanked by diverse classes of modified, highly repetitive DNA

Genome ◽  
1994 ◽  
Vol 37 (4) ◽  
pp. 565-576 ◽  
Author(s):  
Jeffrey L. Bennetzen ◽  
Kathrin Schrick ◽  
Patricia S. Springer ◽  
Willis E. Brown ◽  
Phillip SanMiguel
Keyword(s):  
Repetitive Dna ◽  
Dna Sequences ◽  
Copy Number ◽  
Repetitive Sequences ◽  
Restriction Enzymes ◽  
Single Copy ◽  
Chromosomal Dna ◽  
Coding Regions ◽  
Highly Repetitive Dna ◽  
Copy Dna

We have characterized the copy number, organization, and genomic modification of DNA sequences within and flanking several maize genes. We found that highly repetitive DNA sequences were tightly linked to most of these genes. The highly repetitive sequences were not found within the coding regions but could be found within 6 kb either 3′ or 5′ to the structural genes. These highly repetitive regions were each composed of unique combinations of different short repetitive sequences. Highly repetitive DNA blocks were not interrupted by any detected single copy DNA. The 13 classes of highly repetitive DNA identified were found to vary little between diverse Zea isolates. The level of DNA methylation in and near these genes was determined by scoring the digestibility of 63 recognition/cleavage sites with restriction enzymes that were sensitive to 5-methylation of cytosines in the sequences 5′-CG-3′ and 5′-CNG-3′. All but four of these sites were digestible in chromosomal DNA. The four undigested sites were localized to extragenic DNA within or near highly repetitive DNA, while the other 59 sites were in low copy number DNAs. Pulsed field gel analysis indicated that the majority of cytosine modified tracts range from 20 to 200 kb in size. Single copy sequences hybridized to the unmodified domains, while highly repetitive sequences hybridized to the modified regions. Middle repetitive sequences were found in both domains.Key words: genome organization, interspersed repetitive DNA, DNA modification.

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