Fig. 3. Formation of vault-tubes. (A) SW1573/MVP-GFP cells were incubated at 37°C (a-c), at 21°C for 60 minutes (d-f) and at 37°C for 30 minutes after the treatment at 21°C (g-i). Shown is the MVP-GFP fluorescent signal (a,d,g), the indirect immunofluorescence staining for VPARP (b,e,h) and the merged images (c,f,i). Incubation at 21°C resulted in the formation of large cytoplasmic, tube-like structures (vault-tubes, d). Under the same conditions VPARP staining reveals a dramatic decrease in the number of non-vault-associated VPARP-rods. The VPARP signal almost completely colocalizes with the tube structures (e and f). Both the MVP and VPARP distribution returns to normal when the cells cultured at 21°C were placed at 37°C for 30 minutes (g-i). Bar, 10 µm. (B) Partial colocalization of GFP-tagged MVP (a and d) and the VPARP-rods (b and e) in the merged picture (c and f) after incubation of SW1573/MVP-GFP cells at 21°C for 10 minutes. The arrowheads point to sites where MVP-GFP clusters have formed, which are in close proximity to the VPARP-rods. Bars, 5 µm.