Research article

The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

Victor Yankiwski^1,2 , James P Noonan^1,3 and Norma F Neff¹

¹  Laboratory of Molecular Genetics, New York Blood Center, 310 East 67th Street, New York, NY 10021, USA

²  Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, NJ 07107, USA

³  Department of Genetics, Stanford School of Medicine, Stanford, CA 94305, USA

author email corresponding author email

BMC Cell Biology 2001, 2:11doi:10.1186/1471-2121-2-11

Published:	2 July 2001

Abstract

Background

Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10) or PML (promyelocytic leukemia) nuclear bodies, where it associates with TOPIIIα, and to the nucleolus.

Results

This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities.

Conclusion

The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies.