FIG. 7.
The cysteine residues in Sf-Stk and gp55 are required for Epoind BFU-E colony formation. (A) 293 cells were transfected with MSCV expressing myc-tagged wild-type or mutant forms of Sf-Stk and pEco. At 48 h posttransfection, viral supernatants were collected and incubated overnight with bone marrow cells harvested from C57BL/6 mice. MSCV-infected bone marrow cells were then incubated with FVP on ice for 1 h and plated in methylcellulose medium containing IL-3 (2.5 ng/ml). On day 5, BFU-E colonies were stained with acid-benzidine and counted. *, P < 0.01. Error bars indicate standard deviations. (B) 293 cells were transfected with MSCV expressing wild-type or mutant forms of gp55 and pEco. At 48 h posttransfection, viral supernatants were collected and incubated overnight with bone marrow cells harvested from BALB/c mice. Virus-infected bone marrow cells were then plated in methylcellulose medium containing IL-3 (2.5 ng/ml). On day 5, BFU-E colonies were stained with acid-benzidine and counted. *, P < 0.01.