Fig. 4

hSSB1 protects BLM from proteasomal degradation. a U2OS cells were transfected with control or hSSB1-depleting siRNA, 48 h prior to transfection with an siRNA-resistant HA-tagged hSSB1 plasmid (WT HA hSSB1). Cells were harvested after a further 48 h and whole cell lysates immunoblotted with antibodies against BLM, hSSB1 and actin. BLM levels were determined by densitometry, normalised to the levels of actin and expressed relative to the untreated lane. b U2OS cells were transfected with control or hSSB1-depleting siRNA for 72 h. BLM and hSSB1 mRNA levels were determined by real time PCR and normalised to the mRNA levels of 7SL. The graph represents the results from three independent experiments. A t test was used to assess statistical significance where p < 0.05 was considered significant. n.s. non-significant. c U2OS cells were transfected with control or hSSB1-depleting siRNA, 72 h prior to incubation with 10 μM MG-132 for 6 h. Cells were then lysed and whole cell lysates immunoblotted with antibodies against BLM, hSSB1 and actin. BLM levels were determined by densitometry, normalised to the levels of actin and expressed relative to the untreated lane