Colocalization, Physical, and Functional Interaction between Werner and Bloom Syndrome Proteins

• Published in: The Journal of biological chemistry Vol. 277; no. 24; pp. 22035 - 22044
• Main Authors: von Kobbe, Cayetano, Karmakar, Parimal, Dawut, Lale, Opresko, Patricia, Zeng, Xianmin, Brosh, Jr, Robert M, Hickson, Ian D, Bohr, Vilhelm A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 14.06.2002
• Subjects: Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - metabolism; BLM protein; Bloom's syndrome; Blotting, Western; Cell Line; Cell Nucleus - metabolism; DNA Helicases - chemistry; DNA Helicases - metabolism; Enzyme-Linked Immunosorbent Assay; Exodeoxyribonucleases; HeLa Cells; Humans; Microscopy, Fluorescence; Models, Biological; Phenotype; Precipitin Tests; Protein Binding; Protein Structure, Tertiary; Recombinant Proteins - metabolism; RecQ Helicases; RecQ protein; Werner Syndrome Helicase; Werner's syndrome; WRN protein
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M200914200

The RecQ helicase family comprises a conserved group of proteins implicated in several aspects of DNA metabolism. Three of the family members are defective in heritable diseases characterized by abnormal growth, premature aging, and predisposition to malignancies. These include the WRN and BLM gene products that are defective in Werner and Bloom syndromes, disorders which share many phenotypic and cellular characteristics including spontaneous genomic instability. Here, we report a physical and functional interaction between BLM and WRN. These proteins were coimmunoprecipitated from a nuclear matrix-solubilized fraction, and the purified recombinant proteins were shown to interact directly. Moreover, BLM and WRN colocalized to nuclear foci in three human cell lines. Two regions of WRN that mediate interaction with BLM were identified, and one of these was localized to the exonuclease domain of WRN. Functionally, BLM inhibited the exonuclease activity of WRN. This is the first demonstration of a physical and functional interaction between RecQ helicases. Our observation that RecQ family members interact provides new insights into the complex phenotypic manifestations resulting from the loss of these proteins.