BLM is related to the RecQ subset of DExH box-containing DNA helicases and has both DNA-stimulated ATPase and ATP-dependent DNA 3'-5' helicase activities.It may act to suppress inappropriate DNA recombination. Mutations causing Bloom syndrome delete or alter helicase motifs and may disable the helicase activity.
BLM participates in a supercomplex of BRCA1-associated proteins named BASC (BRCA1-Associated genome Surveillance Complex) containing ATM (defective in ataxia telangiectasia), NBS1 (defective in Nijmegen syndrome) and MRE11 (defective in ataxia-telangiectasia-like disorder), MLH1, MSH2 and MSH6, which are involved in human non-polyposis colorectal cancer, RAD50 and DNA replication factor C.
Defects in BLM are the cause of Bloom syndrome (BLM). BLM is an autosomal recessive disorder characterized by proportionate pre- and postnatal growth deficiency, sun-sensitive telangiectatic hypo- and hyperpigmented skin, predisposition to malignancy, and chromosomal instability.
A few BLM germinal mutations have been described to date. They introduce either amino acid substitutions or premature nonsense codons into the coding sequence; one BLM mutation consisting in a 6 bp deletion accompanied by a 7 bp insertion at nucleic acid position 2281 is common in patients from Ashkenazi Jewish ancestry, leading to a truncated protein of 739 amino acids in length; two BLM mutations, 631delCAA and 1610insA were detected in Japanese patients.
References (open access):
Roles of RECQ helicases in recombination based DNA repair, genomic stability and aging. Singh DK, Ahn B, BohrVA. Biogerontology. 2009 Jun;10(3):235-52.
The human WRN and BLM RecQ helicases differentially regulate cell proliferation and survival after chemotherapeutic DNA damage. Mao FJ, Sidorova JM, Lauper JM, Emond MJ, Monnat RJ. Cancer Res. 2010 Aug 15;70(16):6548-55.