Farah Joseph A, Hartsuiker Edgar, Mizuno Ken-Ichi, Ohta Kunihiro, Smith Gerald R
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
Genetics. 2002 May;161(1):461-8. doi: 10.1093/genetics/161.1.461.
Palindromic sequences can form hairpin and cruciform structures that pose a threat to genome integrity. We found that a 160-bp palindrome (an inverted repeat of 80 bp) conferred a mitotic recombination hotspot relative to a control nonpalindromic sequence when inserted into the ade6 gene of Schizosaccharomyces pombe. The hotspot activity of the palindrome, but not the basal level of recombination, was abolished by a rad50 deletion, by a rad50S "separation of function" mutation, or by a rad32-D25A mutation in the nuclease domain of the Rad32 protein, an Mre11 homolog. We propose that upon extrusion of the palindrome the Rad50.Rad32 nuclease complex recognizes and cleaves the secondary structure thus formed and generates a recombinogenic break in the DNA.
回文序列可形成发夹和十字形结构，对基因组完整性构成威胁。我们发现，当一个160碱基对的回文序列（80碱基对的反向重复序列）插入粟酒裂殖酵母的ade6基因时，相对于对照非回文序列，它赋予了一个有丝分裂重组热点。回文序列的热点活性，而非重组的基础水平，被rad50缺失、rad50S“功能分离”突变或Rad32蛋白（一种Mre11同源物）核酸酶结构域中的rad32 - D25A突变所消除。我们提出，在回文序列挤出后，Rad50.Rad32核酸酶复合物识别并切割由此形成的二级结构，并在DNA中产生一个重组性断裂。
