Telomere repeat DNA forms a large non-covalent complex with unique cohesive properties which is dissociated by Werner syndrome DNA helicase in the presence of replication protein A.

Abstract

We describe the unique structural features of a large telomere repeat DNA complex (TRDC) of >20 kb generated by a simple PCR using (TTAGGG)(4) and (CCCTAA)(4) as both primers and templates. Although large, as determined by conventional agarose gel electrophoresis, the TRDC was found to consist of short single-stranded DNA telomere repeat units of between several hundred and 3000 bases, indicating that it is a non-covalent complex comprising short cohesive telomere repeat units. S1 nuclease digestion showed that the TRDC contains both single- and double-stranded portions stable enough to survive glycerol density gradient centrifugation, precipitation with ethanol and gel electrophoresis. Sedimentation analysis suggests that a part of the TRDC is non-linear and consists of a three-dimensional network structure. After treatment with Werner DNA helicase the TRDC dissociated into smaller fragments, provided that human replication protein A was present, indicating that: (i) the TRDC is a new substrate for the Werner syndrome helicase; (ii) the telomere repeat sequence re-anneals rapidly unless unwound single-stranded regions are protected by replication protein A; (iii) the TRDC may provide a new clue to understanding deleterious telomere-totelomere interactions that can lead to genomic instability. Some properties of the TRDC account for the extra-chromosomal telomere repeat (ECTR) DNA that exists in telomerase-negative immortalized cell lines and may be involved in maintaining telomeres.

• Authors: I Ohsugi, Y Tokutake, N Suzuki, T Ide, M Sugimoto, Y Furuichi
• Journal: Nucleic acids research (Nucleic Acids Res) Vol. 28 Issue 18 Pg. 3642-8 (Sep 15 2000) ISSN: 1362-4962 [Electronic] England
• PMID: 10982887 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA-Binding Proteins
• RPA1 protein, human
• Replication Protein A
• DNA
• Exodeoxyribonucleases
• Single-Strand Specific DNA and RNA Endonucleases
• DNA Helicases
• RecQ Helicases
• WRN protein, human
• Werner Syndrome Helicase

Topics

• Centrifugation, Density Gradient
• DNA (chemistry)
• DNA Helicases (metabolism)
• DNA-Binding Proteins (metabolism)
• Exodeoxyribonucleases
• Humans
• Polymerase Chain Reaction
• Protein Binding
• RecQ Helicases
• Repetitive Sequences, Nucleic Acid
• Replication Protein A
• Single-Strand Specific DNA and RNA Endonucleases (metabolism)
• Telomere
• Werner Syndrome (enzymology, genetics)
• Werner Syndrome Helicase