Langland G, Kordich J, Creaney J, Goss K H, Lillard-Wetherell K, Bebenek K, Kunkel T A, Groden J
Department of Molecular Genetics, Biochemistry, and Microbiology and the Howard Hughes Medical Institute, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
J Biol Chem. 2001 Aug 10;276(32):30031-5. doi: 10.1074/jbc.M009664200. Epub 2001 Apr 26.
Bloom's syndrome (BS) is a rare autosomal recessive disorder characterized by pre- and postnatal growth deficiency, immunodeficiency, and a tremendous predisposition to a wide variety of cancers. Cells from BS individuals are characterized by a high incidence of chromosomal gaps and breaks, elevated sister chromatid exchange, quadriradial formations, and locus-specific mutations. BS is the consequence of mutations that lead to loss of function of BLM, a gene encoding a helicase with homology to the RecQ helicase family. To delineate the role of BLM in DNA replication, recombination, and repair we used a yeast two-hybrid screen to identify potential protein partners of the BLM helicase. The C terminus of BLM interacts directly with MLH1 in the yeast-two hybrid assay; far Western analysis and co-immunoprecipitations confirmed the interaction. Cell extracts deficient in BLM were competent for DNA mismatch repair. These data suggest that the BLM helicase and MLH1 function together in replication, recombination, or DNA repair events independent of single base mismatch repair.
布卢姆综合征（BS）是一种罕见的常染色体隐性疾病，其特征为出生前后生长发育迟缓、免疫缺陷，以及极易患多种癌症。BS患者的细胞具有染色体间隙和断裂发生率高、姐妹染色单体交换增加、四射体形成以及基因座特异性突变等特征。BS是由导致BLM功能丧失的突变引起的，BLM是一种编码与RecQ解旋酶家族具有同源性的解旋酶的基因。为了阐明BLM在DNA复制、重组和修复中的作用，我们利用酵母双杂交筛选来鉴定BLM解旋酶的潜在蛋白质伴侣。在酵母双杂交试验中，BLM的C末端直接与MLH1相互作用；Far Western分析和免疫共沉淀证实了这种相互作用。缺乏BLM的细胞提取物具备DNA错配修复能力。这些数据表明，BLM解旋酶和MLH1在复制、重组或DNA修复事件中共同发挥作用，而与单碱基错配修复无关。
