Evidence that histone H1 is dispensable for proper meiotic recombination in budding yeast

George S Brush

Histone H1, referred to as the linker histone, associates with the nucleosome core particle. While there is indication that the budding yeast version of histone H1 (Hho1) contributes to regulation of chromatin structure and certain chromatin-related processes, such as DNA double-strand break repair, cells lacking Hho1 are healthy and display subtle phenotypes. A recent report has revealed that Hho1 is required for optimal sporulation. The studies described here were conducted to determine whether Hho1 influences meiotic recombination, an event that occurs during sporulation, involves generation and repair of DNA double-strand breaks, and is critical for spore viability. Through tetrad analysis, cells with or without Hho1 were compared for meiotic reciprocal recombination events within several chromosome XV intervals. Parameters investigated included crossover frequency (genetic map distance) and crossover interference. No significant differences were detected between the two cell types. In agreement with earlier studies, spore viability was not affected by Hho1 absence. These data suggest that complete absence of Hho1 from chromatin does not affect reciprocal recombination between homologous chromosomes during meiosis. Therefore, the basal level of Hho1 that remains after its reported depletion early in meiosis is unlikely to be important for regulating recombination. Furthermore, the subsequent accumulation of Hho1 as the haploid products mature does not appear to be crucial for spore viability.