GTPases of the Rac family are important regulators of cytoskeletal remodeling in response to signals received via growth factor responses. The expression patterns of these GTPases are tightly regulated in response to cytochalasin B exposure. In contrast, Rac2 expression is restricted to hematopoietic cells, and is further induced upon terminal myeloid cell differentiation and T cell stimulation. Furthermore, there appears to be cross-talk between the expression of the Rac1 and Rac2 genes, as Rac1 expression is dysregulated in Rac2-null cells.
The specific aims of this proposal are:
(AIM #1) Identify genetic elements and cognate transcription factors responsible for restriction of Rac2 expression to hematopoietic cells. Cytosine methylation patterns and DNase hypersensitive sites surrounding the Rac2 locus will be determined. Bacterial artificial chromosome clones carrying the human Rac2 gene locus will be introduced into mice and murine cell lines, and transgene expression assessed by RNase protection assays in order to identify cis-elements necessary and sufficient to direct lineage-specific expression. In vitro DNA-binding protein assays will be performed to detect and identify transcription factors that interact with critical cis- elements, and novel factors will be molecularly cloned by either ligand screening or biochemical purification approaches.
(AIM #2) Analyze cross-talk between the Rac1 and Rac2 genes. Biochemical studies will be conducted to determine the level at which expression of the Rac1 gene is modulated in response to Rac2 levels. The Rac1 promoter will be cloned and functionally characterized, and critical cis-elements and cognate trans-factors will be identified. The molecular basis for dysregulated Rac1 expression in response to Rac 2 levels will be determined by introducing Rac1 promoter/luciferase reporter genes into primary murine blood cell cultures derived from Rac2-null mice.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Program Projects (P01)
Project #
1P01HL069974-01
Application #
6595700
Study Section
Heart, Lung, and Blood Initial Review Group (HLBP)
Project Start
2002-04-22
Project End
2007-03-31
Budget Start
2002-04-22
Budget End
2003-03-31
Support Year
1
Fiscal Year
2002
Total Cost
$217,365
Indirect Cost
Name
Indiana University-Purdue University at Indianapolis
Department
Type
DUNS #
005436803
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
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Ghiaur, Gabriel; Ferkowicz, Michael J; Milsom, Michael D et al. (2008) Rac1 is essential for intraembryonic hematopoiesis and for the initial seeding of fetal liver with definitive hematopoietic progenitor cells. Blood 111:3313-21
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Thomas, E K; Cancelas, J A; Zheng, Y et al. (2008) Rac GTPases as key regulators of p210-BCR-ABL-dependent leukemogenesis. Leukemia 22:898-904
Li, Yu; Yan, Jingliang; De, Pradip et al. (2007) Rap1a null mice have altered myeloid cell functions suggesting distinct roles for the closely related Rap1a and 1b proteins. J Immunol 179:8322-31
Cheng, Ni; He, Rong; Tian, Jun et al. (2007) A critical role of protein kinase C delta activation loop phosphorylation in formyl-methionyl-leucyl-phenylalanine-induced phosphorylation of p47(phox) and rapid activation of nicotinamide adenine dinucleotide phosphate oxidase. J Immunol 179:7720-8
Thomas, Emily K; Cancelas, Jose A; Chae, Hee-Don et al. (2007) Rac guanosine triphosphatases represent integrating molecular therapeutic targets for BCR-ABL-induced myeloproliferative disease. Cancer Cell 12:467-78
Ming, Wenyu; Li, Shijun; Billadeau, Daniel D et al. (2007) The Rac effector p67phox regulates phagocyte NADPH oxidase by stimulating Vav1 guanine nucleotide exchange activity. Mol Cell Biol 27:312-23
Ghiaur, Gabriel; Lee, Andrew; Bailey, Jeff et al. (2006) Inhibition of RhoA GTPase activity enhances hematopoietic stem and progenitor cell proliferation and engraftment. Blood 108:2087-94

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