Target type: biologicalprocess
A telomere maintenance process that results in the formation of small fragments of circular extrachromosomal DNA elements which contain telomeric DNA. It is speculated that telomeric DNA-containing double minutes are formed through a recombination event between the telomere and chromosome-internal TTAGGG-like sequences. Telomeric DNA-containing double minutes appear as two closely positioned dots in metaphase. [GOC:BHF, GOC:BHF_telomere, GOC:nc, PMID:14690602, PMID:2397458]
Double minutes (DMs) are small, extrachromosomal DNA elements that are frequently observed in cancer cells. They are characterized by their circular structure and contain amplified genes, which can contribute to tumorigenesis. The formation of DMs involving telomeric DNA is a complex process that involves several key steps:
1. **Telomere Replication and Degradation:** During DNA replication, telomeres, the protective caps at the ends of chromosomes, are often incompletely replicated due to the end-replication problem. This can lead to the accumulation of single-stranded DNA overhangs at telomeres.
2. **Telomere Fusion and Breakage:** The single-stranded overhangs can interact with each other, leading to telomere fusions. These fusions are often unstable and can be broken, generating dicentric chromosomes.
3. **Dicentric Chromosome Breakage and DM Formation:** The dicentric chromosomes can undergo breakage, leading to the formation of acentric fragments. These fragments can then circularize, forming DMs. DMs can contain amplified genes, including genes that are involved in cell growth, proliferation, and survival.
4. **DM Replication and Maintenance:** DMs are replicated independently of the host chromosomes. This allows for the amplification of genes that are present on the DMs. DMs are also protected from degradation by specific DNA repair mechanisms.
The formation of telomeric DNA-containing DMs is a complex and dynamic process that is influenced by multiple factors, including telomere length, DNA repair mechanisms, and the activity of specific proteins. The presence of DMs is often associated with poor prognosis in cancer. Further research is needed to fully understand the mechanisms of DM formation and their role in tumorigenesis.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| DNA repair endonuclease XPF | A DNA repair endonuclease XPF that is encoded in the genome of human. [PRO:DNx] | Homo sapiens (human) |
| DNA excision repair protein ERCC-1 | A DNA excision repair protein ERCC-1 that is encoded in the genome of human. [PRO:DNx] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| n-hydroxynaphthalimide | N-hydroxynaphthalimide: structure in first source | ||
| 3-hydroxy-quinazoline-2,4-dione | 3-hydroxy-quinazoline-2,4-dione: structure in first source |