Avian leukemia virus E26 is a replication defective retrovirus that induces a
mixed erythroid/myeloid leukemia in chickens. E26 virus carries two distinct
oncogenes, v-myb and v-ets. The ets portion of this oncogene is required for
the induction of erythroblastosis. V-ets and c-ets-1, its cellular progenitor,
have been shown  to be nuclear DNA-binding proteins. Ets-1 differs slightly
from v-ets at its carboxy-terminal region. In most species where it has been
sequenced, c-ets-1 exists in various isoforms generated by alternative
splicing and differential phosphorylation.
A number of proteins, that share regions of similarity with v-ets/c-ets-1,
have been found and are listed below:
- Ets-2, which has been sequenced in mammals, chicken, Xenopus and
- Human ELF-1, a transcription factor that appears to be required for the T-
cell-receptor-mediated trans activation of HIV-2 genes.
- Mammalian ELK-1, ELK-3 (also known as Net or SAP-2) and ELK-4 (also known
as SRF accessory protein 1 (SAP-1)), which all form a ternary complex with
the serum response factor (SRF).
- Human ERF, a potent transcriptional repressor that binds to the HI element
of the Ets-2 promoter.
- Human ERG.
- Human ERM.
- Mammalian ETV1, a transcriptional activator.
- FLI-1, a sequence specific transcriptional activator.
- Adenovirus E1A enhancer-binding protein (E1A-F) (ETV4) (PEA3).
- PU.1 (also known as Spi-1), a protein that binds to a purine-rich sequence,
the PU-box, that can act as a lymphoid-specific enhancer. PU.1 is probably
a transcriptional activator that may be specifically involved in the
differentiation or activation of macrophages or B cells. In mouse, Spi-1 is
an oncogene involved in murine acute friend erythroleukemia.
- Spi-B, a transcription factor that binds the PU-box.
- GA binding protein (GAPB) α subunit. GAPB is a transcription factor
capable of interacting with purine-rich repeats (GA repeats).
- Drosophila protein elg-1.
- Drosophila protein pokkuri (pok) (also known as yan), which is a negative
regulator of photoreceptor development.
- Drosophila protein pointed (pnt) which is required for glial-neuronal cell
- Drosophila ecdysone induced protein 74E.
All these proteins contain a conserved domain, the 'ETS-domain', [2,3,4,5]
involved in DNA-binding. It seems to recognize purine-rich sequences .
This domain, of about 85 to 90 amino acids, is rich in aromatic and positively
charged residues. It is generally localized at the C-terminus of the protein,
with the exception of ELF-1, ELK-1, ELK-3, ELK-4 and ERF where it is found at
We have derived two signature patterns for the ETS-domain. The first one is
based on a highly conserved region in the N-terminal part of the domain, while
the second is based on a region in the second third of the domain. The profile
spans the complete domain.
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