Differential Activation of M26-Containing Meiotic Recombination Hot Spots in Schizosaccharomyces pombe

Abstract

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.

Linear Element-Independent Meiotic Recombination in Schizosaccharomyces pombe

“…Recombination in the ade6-tps16 interval, situated close to the centromere of chromosome III, was reduced in the rec10-144 mutant to a level similar to that previously reported for the rec10-109 mutant (Figure 2) (De Veaux and Smith 1994). Although the rec10-144 mutant exhibits defects in meiotic recombination at noncentral intervals (see above), this mutant forms LinEs, albeit with a morphological profile very different from the wild type, so may retain some LinE functions (Pryce et al 2005). To explore the question of whether or not LinEs are required for recombination we used an insertion inactivation mutant of rec10, rec10-155 (Lin and Smith 1995), which does not form any detectable LinEs by electron microscopy (Molnar et al 2003) or immunocytochemistry (Lorenz et al 2006).…”

“…However, LinEs form in the rec10-109 mutant during meiosis at the appropriate time, albeit with an altered morphological profile, and may retain some function for activation of recombination (Lorenz et al 2004). Another allele of rec10, rec10-144, has recently been characterized, which resides in a separate complementation group to rec10-109 and is a chemically induced missense mutation (Pryce et al 2005). We noted that crossovers in the leu2-lys7 interval (see Figure 1 for location) on chromosome I were reduced in rec10-144 homozygous zygotic crosses, relative to the rec10 1 control (Figure 2).…”

“…Determination of recombination frequencies: Intragenic recombination frequencies were determined as previously described (Pryce et al 2005). For ura1 and lys7 intragenic recombination uracil-and lysine-deficient media were employed, respectively.…”

Recombination at DNA replication fork barriers is not universal and is differentially regulated by Swi1

“…At this stage the whole colony was placed in 5 ml of appropriate liquid medium and incubated with shaking at 30°C until the early stationary phase. Serial dilutions of cultures were made and plated out onto yeast extract agar (YEA) and YEA containing 20 mg/ml guanine (pH 6.5), which prevents the uptake of adenine because of purine antagonism (45), or onto selective pombe minimal glutamate medium (with and without adenine). Plates were incubated at 33°C for 3 days before counting.…”

Discrepancies Between Recombination Frequencies and Physical Distances in Aspergillus nidulans: Implications for Gene Identification

“…For brevity we give a few examples from fungi but the factors involved affect recombination frequencies across a wide range of organisms. Such factors include environmental influences such as nutritional state (e.g., Abdullah and Borts 2001), genetic factors including both trans-acting genes (e.g., Catcheside 1981; Yeadon et al 2004) and cis-acting recombination hotspots (e.g., Pryce et al 2005;Steiner and Smith 2005), and the long-known effects of chromosomal rearrangements (reviewed by Käfer 1977 andPerkins 1997). These effects can be considerable.…”