Department of Biology, Niagara University, Lewiston, New York 14109, USA.
Genetics. 2011 Feb;187(2):385-96. doi: 10.1534/genetics.110.124636. Epub 2010 Nov 23.
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. Among those sequences we identified some recurring motifs that fell into at least five distinct families, including the well-characterized CRE family of hotspots. Here we report the essential sequence for activity of two of the novel hotspots, the oligo-C and CCAAT hotspots, and identify associated trans-acting factors required for hotspot activity. The oligo-C hotspot requires a unique 8-bp sequence, CCCCGCAC, though hotspot activity is also significantly affected by adjacent nucleotides. The CCAAT hotspot requires a more complex and degenerate sequence, including the originally identified seven nucleotide CCAATCA sequence at its core. We identified transcription factors, the CCAAT-binding factor (CBF) and Rst2, which are required specifically for activity of the CCAAT hotspots and oligo-C hotspots, respectively. Each of these factors binds to its respective motifs in vitro. However, unlike CRE, the sequence required for hotspot activity is larger than the sequence required for binding, suggesting the involvement of additional factors.
在许多生物体中，减数分裂重组优先发生在基因组中称为热点的有限数量的位点上。在裂殖酵母 Schizosaccharomyces pombe 中，简单的序列基序决定了至少一些（可能是大多数或全部）热点的位置。最近，我们表明，大量不同的序列可以创建热点。在这些序列中，我们确定了一些重复出现的基序，这些基序至少属于五个不同的家族，包括特征明确的热点 CRE 家族。在这里，我们报告了两种新型热点（寡聚 C 和 CCAAT 热点）活性的必需序列，并鉴定了与热点活性相关的必需反式作用因子。寡聚 C 热点需要一个独特的 8 个碱基序列 CCCCGCAC，尽管热点活性也受到相邻核苷酸的显著影响。CCAAT 热点需要一个更复杂和退化的序列，包括其核心最初确定的七个核苷酸 CCAATCA 序列。我们鉴定了转录因子 CCAAT 结合因子 (CBF) 和 Rst2，它们分别是 CCAAT 热点和寡聚 C 热点活性所必需的。这些因子中的每一个都在体外与各自的基序结合。然而，与 CRE 不同，热点活性所需的序列大于结合所需的序列，这表明涉及其他因子。
