Overexpression of Gfi1b in a pro-B Abelson murine leukemia virus transformed cell line

We have conducted a screen for factors that downregulate expression of the genes encoding the V(D)J recombinase (RAG1 and RAG2) during B cell development. We have identified the transcription factor Gfi1B as being one of the proteins capable of decreasing RAG transcription when overexpressed in Ableson transormed ProB cell lines. We have yet to determine whether the overexpression of Gfi1B downregulates the RAGs directly, or whether it initiates a signalling programme that results in RAG downregulation. We hypothesize that by comparing global gene expression patterns in cells that overexpress Gfi1B and those that do not, we can distinguish between these possibilities and additionally gain insight into the broader genetic program that may be influenced by Gfi1B during hematopoiesis. Abelson pro-B cells were infected with a retrovirus encoding Gfi1b fused to the estrogen receptor domain. Gfi1b expression was induced by adding tamoxifen to the culture medium for 12h. Three biological replicates of untreated and treated cells were analyzed.