Diverse DNA Sequence Motifs Activate Meiotic Recombination Hotspots Through a Common Chromatin Remodeling Pathway.

In meiosis, multiple different DNA sequence motifs help to position homologous recombination at hotspots in the genome. How do the seemingly disparate -acting regulatory modules each promote locally the activity of the basal recombination machinery? We defined molecular mechanisms of action for five different hotspot-activating DNA motifs (, , , , ) located independently at the same site within the locus of the fission yeast Each motif promoted meiotic recombination (, is active) within this context, and this activity required the respective binding proteins (transcription factors Atf1, Pcr1, Php2, Php3, Php5, Rst2). High-resolution analyses of chromatin structure by nucleosome scanning assays revealed that each motif triggers the displacement of nucleosomes surrounding the hotspot motif in meiosis.

Sequence requirement of the ade6-4095 meiotic recombination hotspot in Schizosaccharomyces pombe.

Homologous recombination occurs at a greatly elevated frequency in meiosis compared to mitosis and is initiated by programmed double-strand DNA breaks (DSBs). DSBs do not occur at uniform frequency throughout the genome in most organisms, but occur preferentially at a limited number of sites referred to as hotspots. The location of hotspots have been determined at nucleotide-level resolution in both the budding and fission yeasts, and while several patterns have emerged regarding preferred locations for DSB hotspots, it remains unclear why particular sites experience DSBs at much higher frequency than other sites with seemingly similar properties.

Unique properties of multiple tandem copies of the M26 recombination hotspot in mitosis and meiosis in Schizosaccharomyces pombe.

The M26 hotspot of the fission yeast Schizosaccharomyces pombe is one of the best-characterized eukaryotic hotspots of recombination. The hotspot requires a seven bp sequence, ATGACGT, that serves as a binding site for the Atf1-Pcr1 transcription factor, which is also required for activity. The M26 hotspot is active in meiosis but not mitosis and is active in some but not all chromosomal contexts and not on a plasmid.

Fission yeast hotspot sequence motifs are also active in budding yeast.

In most organisms, including humans, meiotic recombination occurs preferentially at a limited number of sites in the genome known as hotspots. There has been substantial progress recently in elucidating the factors determining the location of meiotic recombination hotspots, and it is becoming clear that simple sequence motifs play a significant role. In S.

Important characteristics of sequence-specific recombination hotspots in Schizosaccharomyces pombe.

In many organisms, meiotic recombination occurs preferentially at a limited number of sites in the genome known as hotspots. In the fission yeast Schizosaccharomyces pombe, simple sequence motifs determine the location of at least some, and possibly most or all, hotspots. Recently, we showed that a large number of different sequences can create hotspots.

Development of a novel expression, ZI MAX/K ZI, for determination of the counter-anion effect on the antimicrobial activity of tetrabutylammonium salts.

Due to the increasing number of strains of drug-resistant bacteria, the development of new antibiotics has become increasingly important. The antibacterial properties of quaternary amines and their derivatives on both Gram-positive and Gram-negative bacteria are well known. However, an encompassing study with specific emphasis on the role of the counter-anion has not been reported in the literature.

Novel nucleotide sequence motifs that produce hotspots of meiotic recombination in Schizosaccharomyces pombe.

In many organisms, including yeasts and humans, meiotic recombination is initiated preferentially at a limited number of sites in the genome referred to as recombination hotspots. Predicting precisely the location of most hotspots has remained elusive. In this study, we tested the hypothesis that hotspots can result from multiple different sequence motifs.

Multiple modes of chromatin configuration at natural meiotic recombination hot spots in fission yeast.

The ade6-M26 meiotic recombination hot spot of fission yeast is defined by a cyclic AMP-responsive element (CRE)-like heptanucleotide sequence, 5'-ATGACGT-3', which acts as a binding site for the Atf1/Pcr1 heterodimeric transcription factor required for hot spot activation. We previously demonstrated that the local chromatin around the M26 sequence motif alters to exhibit higher sensitivity to micrococcal nuclease before the initiation of meiotic recombination. In this study, we have examined whether or not such alterations in chromatin occur at natural meiotic DNA double-strand break (DSB) sites in Schizosaccharomyces pombe.

Natural meiotic recombination hot spots in the Schizosaccharomyces pombe genome successfully predicted from the simple sequence motif M26.

The M26 hot spot of meiotic recombination in Schizosaccharomyces pombe is the eukaryotic hot spot most thoroughly investigated at the nucleotide level. The minimum sequence required for M26 activity was previously determined to be 5'-ATGACGT-3'. Originally identified by a mutant allele, ade6-M26, the M26 heptamer sequence occurs in the wild-type S.

Activation of an alternative, rec12 (spo11)-independent pathway of fission yeast meiotic recombination in the absence of a DNA flap endonuclease.

Spo11 or a homologous protein appears to be essential for meiotic DNA double-strand break (DSB) formation and recombination in all organisms tested. We report here the first example of an alternative, mutationally activated pathway for meiotic recombination in the absence of Rec12, the Spo11 homolog of Schizosaccharomyces pombe. Rad2, a FEN-1 flap endonuclease homolog, is involved in processing Okazaki fragments.

Optimizing the nucleotide sequence of a meiotic recombination hotspot in Schizosaccharomyces pombe.

The ade6-M26 mutation of Schizosaccharomyces pombe created a meiotic recombination hotspot. Previous analyses indicated that the heptamer 5'-ATGACGT-3' was necessary and sufficient for hotspot activity; the Atf1-Pcr1 transcription factor binds to this sequence and activates M26. After finding cases in which the M26 heptamer in ade6 was, surprisingly, not active as a hotspot, we used an in vitro selection method (SELEX) that revealed an 18-bp consensus sequence for Atf1-Pcr1 binding, 5'-GNVTATGACGTCATNBNC-3', containing the M26 heptamer at its core.

A novel recombination pathway initiated by the Mre11/Rad50/Nbs1 complex eliminates palindromes during meiosis in Schizosaccharomyces pombe.

DNA palindromes are rare in humans but are associated with meiosis-specific translocations. The conserved Mre11/Rad50/Nbs1 (MRN) complex is likely directly involved in processing palindromes through the homologous recombination pathway of DNA repair. Using the fission yeast Schizosaccharomyces pombe as a model system, we show that a 160-bp palindrome (M-pal) is a meiotic recombination hotspot and is preferentially eliminated by gene conversion.

Meiotic DNA breaks at the S. pombe recombination hot spot M26.

The ade6-M26 allele of Schizosaccharomyces pombe creates a well-defined meiotic recombination hot spot that requires a specific sequence, 5'-ATGACGT-3', and the Atf1*Pcr1 transcription factor for activity. We find that M26 stimulates the formation of meiosis-specific double-strand DNA breaks at multiple sites surrounding M26. Like hot spot activity, breakage requires the M26 heptamer, Pcr1, and the general recombination factor Rec12.

Meiotic recombination remote from prominent DNA break sites in S. pombe.

DNA breakage is intimately associated with meiotic recombination in the fission yeast Schizosaccharomyces pombe. Sites of prominent DNA breakage were found approximately 25 to approximately 200 kb apart in the genomic regions surveyed. We examined in detail a 501 kb region of chromosome I and found six sites, or tight clusters of sites, at which approximately 2%-11% of the DNA accumulated breaks in a rad50S mutant.