The overall goal of this project is to understand the molecular mechanisms by which the c-myb proto-oncogene regulates normal and malignant hematopoiesis. We have recently shown that constitutive overexpression of the c-Myb protein is not sufficient to transform normal hematopoietic cells. In contrast, truncation of either the amino (N-) or the carboxyl (C-) terminus of c-Myb results in the transformation of promyelocytes (granulocyte precursors), whereas simultaneous truncation of both the N- and C-termini of c-Myb results in the transformation of myeloblasts (promyelocyte precursors). Both of these phenotypes differ from that of the monoblasts (macrophage precursors) transformed by the doubly truncated v-Myb protein of the avian myeloblastosis virus that contains eleven amino acid substitutions relative to c-Myb. We have also shown that the fusion of either the N- or C- terminus of c-Myb to the v-Myb protein suppresses transformation. These results imply that both the N- and C-termini of c- Myb can act as negative regulatory domains. The ability of different forms of c-Myb to transform different types of cells also suggests that c-Myb itself may participate in the control of hematopoietic lineage determination. This hypothesis is supported by the recent demonstration that mice with a homozygous disruption of c-myb are defective in fetal hematopoiesis. Accordingly, our specific aims for the next five years are as follows: (l) To precisely define which structural features of the N- and C-termini of c-Myb must be altered to cause transformation and alter lineage determination. (2) To determine the effects of alterations of the N- and C-termini of c- Myb on protein conformation, DNA-binding, and transcriptional regulation. (3) To determine the effects of alternatively spliced exons on the function of normal and altered forms o c-Myb. (4) To use high frequency homologous recombination in clonal chicken B cell lines to directly examine the role of c-Myb in hematopoietic lineage determination. (5) To analyze hematopoietic and lymphoid differentiation in transgenic lines of mice that express various forms of c-Myb, including the tissue- specific expression of dominant inhibitors of Myb function.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA056509-02
Application #
2097355
Study Section
Virology Study Section (VR)
Project Start
1994-01-01
Project End
1998-12-31
Budget Start
1995-01-01
Budget End
1995-12-31
Support Year
2
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Stanford University
Department
Pathology
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Davidson, Colin J; Tirouvanziam, Rabindra; Herzenberg, Leonard A et al. (2005) Functional evolution of the vertebrate Myb gene family: B-Myb, but neither A-Myb nor c-Myb, complements Drosophila Myb in hemocytes. Genetics 169:215-29
Tirouvanziam, Rabindra; Davidson, Colin J; Lipsick, Joseph S et al. (2004) Fluorescence-activated cell sorting (FACS) of Drosophila hemocytes reveals important functional similarities to mammalian leukocytes. Proc Natl Acad Sci U S A 101:2912-7
Wang, D M; Dubendorff, J W; Woo, C H et al. (1999) Functional analysis of carboxy-terminal deletion mutants of c-Myb. J Virol 73:5875-86
Dubendorff, J W; Lipsick, J S (1999) Transcriptional regulation by the carboxyl terminus of c-Myb depends upon both the Myb DNA-binding domain and the DNA recognition site. Oncogene 18:3452-60
Woo, C H; Sopchak, L; Lipsick, J S (1998) Overexpression of an alternatively spliced form of c-Myb results in increases in transactivation and transforms avian myelomonoblasts. J Virol 72:6813-21
Ganter, B; Fu, S l; Lipsick, J S (1998) D-type cyclins repress transcriptional activation by the v-Myb but not the c-Myb DNA-binding domain. EMBO J 17:255-68
Fu, S L; Lipsick, J S (1997) Constitutive expression of full-length c-Myb transforms avian cells characteristic of both the monocytic and granulocytic lineages. Cell Growth Differ 8:35-45
Dini, P W; Eltman, J T; Lipsick, J S (1995) Mutations in the DNA-binding and transcriptional activation domains of v-Myb cooperate in transformation. J Virol 69:2515-24