A multiprotein nuclear complex connects Fanconi anemia and Bloom syndrome.
Bloom syndrome (BS) is a genetic disorder associated with dwarfism, immunodeficiency, reduced fertility, and an elevated risk of cancer. To investigate the mechanism of this disease, we isolated from human HeLa extracts three complexes containing the helicase defective in BS, BLM. Interestingly, one of the complexes, termed BRAFT, also contains five of the Fanconi anemia (FA) complementation group proteins (FA proteins). FA resembles BS in genomic instability and cancer predisposition, but most of its gene products have no known biochemical activity, and the molecular pathogenesis of the disease is poorly understood. BRAFT displays a DNA-unwinding activity, which requires the presence of BLM because complexes isolated from BLM-deficient cells lack such an activity. The complex also contains topoisomerase IIIalpha and replication protein A, proteins that are known to interact with BLM and could facilitate unwinding of DNA. We show that BLM complexes isolated from an FA cell line have a lower molecular mass. Our study provides the first biochemical characterization of a multiprotein FA complex and suggests a connection between the BLM and FA pathways of genomic maintenance. The findings that FA proteins are part of a DNA-unwinding complex imply that FA proteins may participate in DNA repair.
Laboratory of Genetics. Mass Spectrometry Unit, National Institute on Aging/NIH, TRIAD Center Room 3000, 333 Cassell Drive, Baltimore, MD 21224, USA.
Amom Ruhikanta
AR
Meetei
Salvatore
S
Sechi
Michael
M
Wallisch
Dafeng
D
Yang
Mary K
MK
Young
Hans
H
Joenje
Maureen E
ME
Hoatlin
Weidong
W
Wang
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001816:Bloom Syndrome / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism; D004260:DNA Repair; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005199:Fanconi Anemia / Q000235:genetics* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D011233:Precipitin Tests; D053484:RecQ Helicases; D051716:Replication Protein A; D025801:Ubiquitin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D004268:DNA-Binding Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D025801:Ubiquitin; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I