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Mol. Cell. Biol., 03 1997, 1503-1512, Vol 17, No. 3
X Fu and MP Kamps
The E2a-Pbx1 oncoprotein contains the transactivation domain of E2a joined
to the DNA-binding homeodomain (HD) of Pbx1. In mice, E2a-Pbx1 transforms T
lymphoblasts and fibroblasts and blocks myeloblast differentiation. Pbx1
and E2a-Pbx1 bind DNA as heterodimers with other HD proteins whose
expression is tissue specific. While the transactivation domain of E2a is
required for all forms of transformation, DNA binding by the Pbx1 HD is
essential for blocking myeloblast differentiation but dispensable for
fibroblast or T- lymphoblast transformation. These properties suggest (i)
that E2a-Pbx1 causes cellular transformation by activating gene
transcription, (ii) that transcription of E2a-Pbx1 target genes is normally
regulated by ubiquitous Pbx proteins and tissue-specific partners, and
(iii) that DNA-binding mutants of E2a-Pbx1 activate a subset of all gene
targets. To test these predictions, genes induced in NIH 3T3 fibroblasts by
E2a- Pbx1 were identified and examined for tissue- and stage-specific
expression and their differential abilities to be upregulated by E2a- Pbx1
in NIH 3T3 fibroblasts and myeloblasts and by a DNA-binding mutant of
E2a-Pbx1 in NIH 3T3 cells. Of 12 RNAs induced by E2a-Pbx1, 4 encoded known
proteins (a J-C region of the immunoglobulin kappa light chain, natriuretic
peptide receptor C, mitochondrial fumarase, and the 3',5'- cyclic
nucleotide phosphodiesterase, PDE1A) and 5 encoded new proteins related to
angiogenin, ion channels, villin, epidermal growth factor repeat proteins,
and the human 2.19 gene product. Expression of many of these genes was
tissue specific or developmentally regulated, and most were not expressed
in fibroblasts, indicating that E2a-Pbx1 can induce ectopic expression of
genes associated with lineage-specific differentiation.
Copyright © 1997, American Society for Microbiology
E2a-Pbx1 induces aberrant expression of tissue-specific and developmentally regulated genes when expressed in NIH 3T3 fibroblasts
Department of Pathology, University of California, San Diego, School of Medicine, La Jolla 92093, USA.
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