EC Number   |
Substrates |
Organism |
Products |
Reversibility |
|---|
   5.6.2.1 | (TTA)35 |
trinucleotide repeat (TTA)35 lying in the intergenic region of chromosome XIII of Saccharomyces cerevisiae, between the RPM2 (RNase P mitochondrial 2) and PRE8 genes. This sequence contains the structural elements suitable to be susceptible to DNA topoisomerase I site-specific activity and to assemble nucleosomes. DNA topoisomerase I strongly recognizes the TTA repeats. The (TTA)35 repeat is engaged in a positioned nucleosome in vivo. DNA topoisomerase I efficiently reacts with the TTA repeat, the (TTA)35 sequence, the longest and most stable among the simple repeated sequences in Saccharomyces cerevisiae, is organized in a positioned nucleosome and this can possibly account for its high stability, in fact each nucleosome stores one negative supercoil, thus preventing DNA denaturation and induction of conformational alterations responsible for genetic instability. DNA topoisomerase I in vivo cleaves the (TTA)35 sequence after nucleosome removal, the positioned nucleosome on the (TTA)35 sequence represents a hindrance to the DNA topoisomerase I activity. This last conclusion, based on the glucose/galactose experiments, represents the first formal evidence that DNA topoisomerase I cannot react with nucleosomal DNA |
Saccharomyces cerevisiae |
? |
- |
? |
| 5.6.2.1 | 117-base pair DNA oligonucleotide |
- |
Homo sapiens |
? |
- |
? |
| 5.6.2.1 | DNA |
specific for single-stranded DNA, the enzyme drives extensive unwinding of closed circular DNA at high temperature. At 60-80°C it relaxes negatively but not positively supercoiled DNA. At 95°C, the enzyme unwinds both positively and negatively supercoiled substrates and produces extensively unwound form I* and I** DNA |
Desulfurococcus amylolyticus |
? |
- |
? |
| 5.6.2.1 | DNA |
the enzyme exhibits a very high DNA relaxing activity. Strong preference for a cytosine at position -4 of the cleavage |
Thermotoga maritima |
? |
- |
? |
| 5.6.2.1 | DNA |
the enzyme exhibits a very high DNA relaxing activity. Strong preference for a cytosine at position -4 of the cleavage |
Thermotoga maritima DSM 3109 |
? |
- |
? |
| 5.6.2.1 | DNA |
specific for single-stranded DNA, the enzyme drives extensive unwinding of closed circular DNA at high temperature. At 60-80°C it relaxes negatively but not positively supercoiled DNA. At 95°C, the enzyme unwinds both positively and negatively supercoiled substrates and produces extensively unwound form I* and I** DNA |
Desulfurococcus amylolyticus DSM 3822 |
? |
- |
? |
| 5.6.2.1 | DNA |
so-called suicide substrate, contains a htopoI preferential binding sequence and is designed to trap the liberated 5'-OH end |
Homo sapiens |
DNA |
- |
? |
| 5.6.2.1 | Holliday Junction Substrate H1-4 |
close relationship between tyrosine recombinases and type IB topoisomerases, investigation of ability of human topoisomerase I to resolve the typical intermediate of recombinase catalysis, the Holliday junction, results consolidate the relationship between type IB topoisomerases and tyrosine recombinases |
Homo sapiens |
? |
- |
? |
| 5.6.2.1 | more |
- |
eukaryota |
? |
- |
? |
| 5.6.2.1 | more |
- |
Drosophila sp. (in: flies) |
? |
- |
? |
