This section is interested in transcription factors that regulate the development of the immune system. IRF-8/ICSBP, a DNA specific transcription factor is essential for the development of macrophages and dendritic cells. In addition to their development, IRF-8 controls the expression of interferons and the IL-12 cytokine in these cells, thereby playing a critical role in the establishment of innate immunity. To address the mechanism of IRF-8 action, we performed photobleaching experiments. We show that IRF-8 is moving rapidly in the nucleus and scanning the entire genome by transiently binding to chromatin in macrophages and DCs. Further analysis showed that IRF-8 chromatin interactions are regulated by external cytokine signaling. This study opened a new way to study transcription in living immune cells. Another model we investigate deals with a bromodomain protein Brd4. This protein binds to acetylated chromatin and associates with chromosomes during mitosis. Brd4 is thought to play a role in epigenetic memory. We found that Brd4 interacts with P-TEFb, a Cdk9/CyclinT heterodimer that is essential for RNA polymerase II transcriptional elongation. By chromatin immunoprecipitation analysis of the HIV-1LTR reporter, we provided evidence that Brd4 recruits P-TEFb to the promoter to stimulate transcription. These studies have unraveled a previously unknown role for Brd4 in transcription.

Project Start
Project End
Budget Start
Budget End
Support Year
20
Fiscal Year
2006
Total Cost
Indirect Cost
Name
U.S. National Inst/Child Hlth/Human Dev
Department
Type
DUNS #
City
State
Country
United States
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Umehara, Takashi; Nakamura, Yoshihiro; Wakamori, Masatoshi et al. (2010) Structural implications for K5/K12-di-acetylated histone H4 recognition by the second bromodomain of BRD2. FEBS Lett 584:3901-8
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Dror, Natalie; Alter-Koltunoff, Michal; Azriel, Aviva et al. (2007) Identification of IRF-8 and IRF-1 target genes in activated macrophages. Mol Immunol 44:338-46

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