The first membrane spanning region of the lamin B receptor is sufficient for sorting to the inner nuclear membrane

CCS-1 cells were maintained in DME (Gibco Laboratories, Grand Island, NY) supplemented with 10% F'CS (Gibco Laboratories). Cells were transfected using the calcium phosphate transfection protocol of Chen and Ckyama, (1987) . For immunoituorescence experiments, CCS-1 cells were plated on coverslips in 16-ram wells ('~50% confluent) and transfected with 1/~g of supercoiled DNA which was purified on Qiagen columns (Qingen, Chatsworth, CA) according to the suppliers protocol. Cells were analyzed by indirect immunofluorescence microscopy 24-40 h aider transfection. The number of ceils expressing the transfected protein ranged from 5% to 40% depending on the construct.