InterPro domain: IPR034136

This topoisomerase-primase (TOPRIM) nucleotidyl transferase/hydrolase domain is found in the type II topoisomerase VIA and Spo11. This subgroup contains proteins similar to Sulfolobus shibatae topoisomerase VIA (TopoVIA) [ 1 ] and Saccharomyces cerevisiae meiotic recombination factor Spo11 [ 2 ]. Type II DNA topoisomerases catalyze the ATP-dependent transport of one DNA duplex through another, in the process generating transient double strand breaks via covalent attachments to both DNA strands at the 5' positions. TopoVI enzymes are heterotetramers found in archaea and plants [ 3 , 4 ]. Spo11 plays a role in generating the double strand breaks that initiate homologous recombination during meiosis [ 5 , 6 ]. S. shibatae TopoVI relaxes both positive and negative supercoils, and in addition has a strong decatenase activity [ 7 ].

The TOPRIM domain has two conserved motifs, one of which centres at a conserved glutamate and the other one at two conserved aspartates (DxD). For topoisomerases, the conserved glutamate is believed to act as a general base in strand joining, and as a general acid in strand cleavage [ 8 ]. The DXD motif may co-ordinate Mg2+, a cofactor required for full catalytic function.

1. Purification of a DNA topoisomerase II from the hyperthermophilic archaeon Sulfolobus shibatae. A thermostable enzyme with both bacterial and eucaryal features. J. Biol. Chem. 269, 27663-9
2. Meiotic recombination: breaking the genome to save it. Curr. Biol. 11, R253-6
3. Emerging roles for plant topoisomerase VI. Chem. Biol. 10, 107-11
4. Molecular characterization of homologues of both subunits A (SPO11) and B of the archaebacterial topoisomerase 6 in plants. Gene 271, 81-6
5. Identification of residues in yeast Spo11p critical for meiotic DNA double-strand break formation. Mol. Cell. Biol. 22, 1106-15
6. Distinct functions of S. pombe Rec12 (Spo11) protein and Rec12-dependent crossover recombination (chiasmata) in meiosis I; and a requirement for Rec12 in meiosis II. Cell Chromosome 1, 1
7. Structure and function of an archaeal topoisomerase VI subunit with homology to the meiotic recombination factor Spo11. EMBO J. 18, 6177-88
8. Toprim--a conserved catalytic domain in type IA and II topoisomerases, DnaG-type primases, OLD family nucleases and RecR proteins. Nucleic Acids Res. 26, 4205-13