BLM helicase as a mousetrap
Robert Brosh, Jr. wrote an article on Nature about the BLM helicase [Nature 456, 453-454 (27 November 2008) | doi:10.1038/456453a; Published online 26 November 2008]. His introductory paragraph goes:
“Bloom’s syndrome, which is characterized by severe growth retardation, immunodeficiency, anaemia, reduced fertility and predisposition to cancer1, is caused by mutations in the gene BLM. At the cellular level, the hallmark of this genetic disorder is a high rate of sister-chromatid exchange — the swapping of homologous stretches of DNA between a chromosome and its identical copy generated during DNA replication2. Understanding how mutations in BLM lead to this chromosomal abnormality has been of considerable interest to both scientists and clinicians. So the latest clue to solving the mystery of Bloom’s syndrome, which Xu et al.3 and Singh et al.4 report in Genes & Development, is a welcome advance.”
The BLM protein complex consists of several components, much like a mousetrap. With all the parts properly assembled, the mousetrap will operate efficiently and catch the mouse. In this case, a DNA structure called a double Holliday junction is caught in the BLM complex. Xu et al.3 and Singh et al.4 report the discovery of a component of this complex, RMI2, which stabilizes and orchestrates the action of the BLM complex, ensuring resolution of the double Holliday junction, and so promoting chromosomal stability
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