Globin genes are expressed exclusively in the erythroid lineage, and at distinct stages of development. The mechanisms by which the globin genes are regulated are of interest because a more detailed knowledge of the process is likely to contribute to therapies for severe hemoglobinopathies such as thalassemia and sickle cell disease, and because the globin genes are classic models of complex multigene regulation. Our long-term goal is to understand how the globin genes are expressed only in red blood cells, and how the individual genes are controlled through development. During erythroid differentiation, there is a progressive condensation of chromatin in the nucleus culminating in complete cessation of transcription; the globin genes continue to be transcribed until late in this process. We study a nuclear factor, GATA- 1, that appears to have a central role in the expression of globins and other typically erythroid genes in the terminal phase of erythroid differentiation at all stages of development. We have developed a model in which GATA-1 serves to keep globins and other erythroid genes in an active state while genes not essential for the erythroid program are repressed. To test this hypothesis we have developed an assay that uses the beta-geo reporter to distinguish effects on the level of gene expression from effects on epigenetic stability; previous studies of gene regulation have not separated these two parameters. We propose to investigate the interaction of erythroid transcriptional control elements with chromatin, using the beta-geo assay in conjunction with site- specific recombination to control for position effects. We will dissect the gamma-globin promoter, asking which elements within it regulate the level of gene expression and which counteract repression. We will continue our study of the 5'HS2 globin enhancer, in which we have shown that it acts primarily to relieve repression, and focus on the contribution of its component elements to its function. We will also analyze the role of the chromatin factor HMG-l in developmental regulation of the gamma-globin gene, and the expression of repressive chromatin proteins in the terminal phase. Ultimately we hope that these studies will lead to better understanding of developmental regulation of the globin genes and improved therapies for the hemoglobinopathies..

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL048790-07
Application #
2735205
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1992-08-01
Project End
2000-06-30
Budget Start
1998-07-01
Budget End
1999-06-30
Support Year
7
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Fred Hutchinson Cancer Research Center
Department
Type
DUNS #
075524595
City
Seattle
State
WA
Country
United States
Zip Code
98109
Bigas, A; Martin, D I; Milner, L A (1998) Notch1 and Notch2 inhibit myeloid differentiation in response to different cytokines. Mol Cell Biol 18:2324-33
Sutherland, H G; Martin, D I; Whitelaw, E (1997) A globin enhancer acts by increasing the proportion of erythrocytes expressing a linked transgene. Mol Cell Biol 17:1607-14
Walters, M; Andrews, N C; Magis, W et al. (1996) Erythroid AP-1/NF-E2 elements vary in their response to NF-E2. Exp Hematol 24:445-52
Martin, D I; Whitelaw, E (1996) The vagaries of variegating transgenes. Bioessays 18:919-23
Magis, W; Martin, D I (1995) HMG-I binds to GATA motifs: implications for an HPFH syndrome. Biochem Biophys Res Commun 214:927-33
Fiering, S; Epner, E; Robinson, K et al. (1995) Targeted deletion of 5'HS2 of the murine beta-globin LCR reveals that it is not essential for proper regulation of the beta-globin locus. Genes Dev 9:2203-13
Walters, M; Martin, D I (1992) Functional erythroid promoters created by interaction of the transcription factor GATA-1 with CACCC and AP-1/NFE-2 elements. Proc Natl Acad Sci U S A 89:10444-8