FIG. 2.
Inducible human E47 rescues Igκ germ line transcription and recombination. (A) E47R is sufficient to activate Igκ germ line transcription. Total RNA was isolated from E2A+/+ or E2A−/− Ab-MuLV pre-B cells treated with 1 μM tamoxifen (tamox) and E47R-reconstituted Ab-MuLV B cells treated with 0.1% DMSO or 1 μM tamoxifen for 6 h. Semiquantitative RT-PCR was performed to determine the relative level of Igκ germ line transcription (Igκ-GL). EF1α serves as a positive loading control, and results are presented as threefold serial dilutions. (B) E47R promotes Igκ recombination. E47R-reconstituted pre-B cells were treated with 1 μM tamoxifen or 0.1% DMSO for 8 or 24 h. Genomic DNA was prepared from the cells, and the accumulation of Jκ1 signal break ends (SBE) was determined by LM-PCR. PCR amplification of the CD14 gene serves as a control for DNA loading and quality. (C) Igκ germ line transcription is dependent on E2A. E47R-reconstituted pre-B cells were treated with 1 μM tamoxifen for 6 h, washed, and cultured without tamoxifen. Total RNA was prepared at the indicated times after the removal of tamoxifen. Mock-treated cells were cultured in the presence of 0.1% DMSO for the entire duration of the experiment. Relative abundance of Igκ germ line transcript and EF1α transcript was determined by RT-PCR.