c‐Myb is a transcription factor and proto‐oncogene that is important for hematopoietic cell differentiation. The regulation of the c‐Myb protein and its down stream targets is well studied while the regulation of expression of the c‐myb gene is not well understood. c‐myb expression is controlled by a conditional block in transcriptional elongation in the first intron of the gene. Previous studies have shown that NF‐kB family members are involved in regulating the activation of c‐myb by binding to Rel‐Related Proteins Binding Elements (RRBE) in the first intron. This leads to the hypothesis that NF‐kB regulates expression of c‐myb during development of hematopoietic cells. Here we show using chromatin immunoprecipitations (ChIPs) and real‐time PCR in murine erythroleukemia cells that the down regulation of c‐myb expression via hexamethylene bisacetamide‐induced differentiation can be over‐come by activation of adenyl cyclase by forskolin. ChIP results demonstrate a correlation between occupancy of the RRBE sites by the p65 subunit of NF‐kB with elevated c‐myb mRNA levels. This study demonstrates for the first time a correlation between NF‐kB occupancy of RRBE sites and c‐myb expression in vivo in hematopoietic cells. Research support provided by a Providence College Committee on Aid to Faculty Research Grant.

c‐Myb is a transcription factor and proto‐oncogene that is important for hematopoietic cell development. This gene is predominately expressed in progenitor cells of adult bone marrow and down regulated during differentiation. Through gene knockout experimentation, the importance for c‐myb in developing cells has been determined. Null mutants show lethality in certain blood cell lines, strengthening the ideas that c‐myb plays an important role in cell line differentiation. Specifically, in murine embryonic cells, the absence of c‐myb results in the disruption of specific blood cell types. Previous studies have shown that NF‐κB family members are involved in regulating the activation of c‐myb by binding to Rel‐Related Proteins Binding Elements (RRBE) in the first intron. This leads to the hypothesis that NF‐kB regulates expression of c‐myb during development of hematopoietic cells. We have set up an in vitro differentiation protocol for differentiating induced pluripotent stem cells into blood cell precursors via a hemangioblast intermediate using defined cytokine and growth factors. Activation of c‐myb and NF‐kB was analyzed using qPCR to analyze the kinetics of c‐myb expression. Work is continuing using mobility shift assays and chromatin immunoprecipitations to determine the localization of NF‐kB to the c‐myb locus. Research support provided by a Providence College Committee on Aid to Faculty Research Grant.