Differential activation of M26-containing meiotic recombination hot spots in Schizosaccharomyces pombe.

Certain genomic loci, termed hot spots, are predisposed to undergo genetic recombination during meiosis at higher levels relative to the rest of the genome. The factors that specify hot-spot potential are not well understood. The M26 hot spot of Schizosaccharomyces pombe is dependent on certain trans activators and a specific nucleotide sequence, which can function as a hot spot in a position- and orientation-independent fashion within ade6. In this report we demonstrate that a linear element (LE) component, Rec10, has a function that is required for activation of some, but not all, M26-containing hot spots and from this we propose that, with respect to hot-spot activity, there are three classes of M26-containing sequences. We demonstrate that the localized sequence context in which the M26 heptamer is embedded is a major factor governing whether or not this Rec10 function is required for full hot-spot activation. Furthermore, we show that the rec10-144 mutant, which is defective in full activation of ade6-M26, but proficient for activation of other M26-containing hot spots, is also defective in the formation of LEs, suggesting an intimate link between higher-order chromatin structure and local influences on hot-spot activation.