BLM helicase stimulates the ATPase and chromatin-remodeling activities of RAD54

Abstract

Mutation of BLM helicase results in the autosomal recessive disorder Bloom syndrome (BS). Patients with BS exhibit hyper-recombination and are prone to almost all forms of cancer. BLM can exhibit its anti-recombinogenic function either by dissolution of double Holliday junctions or by disruption of RAD51 nucleofilaments. We have now found that BLM can interact with the pro-recombinogenic protein RAD54 through an internal ten-residue polypeptide stretch in the N-terminal region of the helicase. The N-terminal region of BLM prevented the formation of RAD51-RAD54 complex, both in vitro and in vivo. Using the fluorescence recovery after photobleaching (FRAP) technique, we found that RAD54 and BLM rapidly and concurrently, yet transiently, bound to the chromatinized foci. Presence of BLM enhanced the mobility of both soluble and chromatinized RAD51 but not RAD54. The BLM-RAD54 interaction could occur even in absence of functional RAD51. The N-terminal 1-212 amino acids of BLM or an ATPase-dead mutant of the full-length helicase enhanced the ATPase and chromatin-remodeling activities of RAD54. These results indicate that apart from its dominant function as an anti-recombinogenic protein, BLM also has a transient pro-recombinogenic function by enhancing the activity of RAD54.

The Bloom Syndrome Protein Limits the Lethality Associated with RAD51 Deficiency

“…1D and data not shown). Excess SCE in BLM-deficient cells has been shown to be recombination dependent (2,3). We found that RAD51 downregulation decreased the frequency of SCEs to wild-type levels in BLM-depleted cells (Fig.…”

“…SCEs are mediated by homologous recombination (HR; refs. [2][3][4]. BLM deficiency is associated with replication abnormalities and an increase in HR (1).…”

Dynamics of the DNA repair proteins WRN and BLM in the nucleoplasm and nucleoli

“…Assuming that the fusion protein (e.g. EGFP-WRN) is spherical, from the scaling above the diffusion coefficient of the fusion protein is estimated by use of the equation: $$D_{\text{fusion protein}}=\sqrt[3]{\frac{M_{\text{GFP}}}{M_{\text{fusion protein}}}}{D}_{\text{GFP}}$$ where D GFP is 28 μm 2 /s (Shiratori et al 2002; Braga and McNally 2007; Huranová et al 2010; Grierson et al 2012), M GFP is 27 kDa (Braga and McNally 2007; Compton et al 2008; Van Royen et al 2011), M WRN = 165 kDa (Houtsmuller et al 1999; Compton et al 2008; Srivastava et al 2009), and M BLM = 170 kDa (Erickson 2009; Srivastava et al 2009). To account for possible deviations from spherical shape we follow Erickson (2009) and Spiess and Neumeyer (2010) and reduce the theoretically estimated diffusion coefficient by 20 %, corresponding to a shape-correction factor for globular proteins.…”

Enhancement of c-Myc degradation by Bloom (BLM) helicase leads to delayed tumor initiation

“…Recombinants and siRNA pGEX4T-1 BLM (1-1417) (Srivastava et al, 2009), pGEX4T-1 BLM (1-212), pcDNA3 Flag BLM (gift from Ian Hickson), EGFP-C1 BLM (gift from Nathan Ellis), pGEX4T-1 BLM (191-660), pGEX4T-1 BLM (621-1041), pGEX4T-1 BLM (1001-1417) (Tripathi et al, 2008). pSG5-Jun (gift from Bohdan Wasylyk).…”