An atypical topoisomerase II from archaea with implications for meiotic recombination

Abstract

Type II topoisomerases help regulate DNA topology during transcription, replication and recombination by catalysing DNA strand transfer through transient double-stranded breaks. All type II topoisomerases described so far are members of a single protein family. We have cloned and sequenced the genes encoding the A and B subunits of topoisomerase II from the archaeon Sulfolobus shibatae. This enzyme is the first of a new family. It has no similarity with other type II topoisomerases, except for three motifs in the B subunit probably involved in ATP binding and hydrolysis. We also found these motifs in proteins of the Hsp90 and MutL families. The A subunit has similarities with four proteins of unknown function. One of them, the Saccharomyces cerevisiae Spo11 protein, is required for the initiation of meiotic recombination. Mutagenesis, performed on SPO11, of the single tyrosine conserved between the five homologues shows that this amino acid is essential for Spo11 activity. By analogy with the mechanism of action of known type II topoisomerases, we suggest that Spo11 catalyses the formation of double-strand breaks that initiate meiotic recombination in S. cerevisiae.

Differential gene expression of mammalian SPO11/TOP6A homologs during meiosis1

“…One region (block A in Fig. 1) contains a tyrosine that is present in all functional homologs and, when mutated in budding yeast, results in the loss of DSB activity [6]. A second region (blocks B^D) shares homology with the Toprim domain common to topoisomerase and DNA primase enzymes, which may participate in cleavage and/or rejoining reactions by coordinating Mg 2 ions [23].…”

“…However, the protein that is responsible for meiotic DSB formation, SPO11, was only recently isolated on the basis of its covalent linkage to the 5P ends of DSBs in yeast meiotic cells [5]. SPO11 was shown to be structurally similar to the A subunit of topoisomerase VI (TOP6A), a type II topoisomerase that has been found only in archaea [6,7]. Although this structural similarity is consistent with a role for SPO11 as the enzyme that catalyzes meiosis-speci¢c DSBs, enzymatic activity for yeast or other eukaryotic SPO11 proteins has not been demonstrated.…”

A DNA binding motif of meiotic recombinase Rec12 (Spo11) defined by essential glycine-202, and persistence of Rec12 protein after completion of recombination

“…The fission yeast Rec12 protein (Spo11 in budding yeast) is a meiosis-specific ortholog of the catalytic subunit (Top6A) of a type VI topoisomerase (Bergerat et al, 1997;Keeney et al, 1997;Sharif et al, 2002) and is thought to catalyze the formation of dsDNA breaks that initiate recombination (reviewed in Keeney, 2001). The breaks are processed to form 3VssDNA tails which initiate recombinational repair from a homologous chromatid (Sun et al, 1989;Cao et al, 1990;Schwacha and Kleckner, 1995).…”

TopoVIL

“…Dans la première, il a été montré que la protéine Spo11 était l'homologue de la sous-unité catalytique (A) de la topoisomérase TopoVI de l'archée 1 Sulfolobus shibatae (TopoVIA). Les auteurs de cette étude ont, de plus, montré que la tyrosine catalytique de TopoVIA était conservée dans la séquence de Spo11 et ont démontré, par mutagenèse dirigée, que cette tyrosine était essentielle à la formation des CDB méiotiques chez la levure [7]. Les TopoVI sont des topoisomérases de type II.…”