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E2A: master regulator of B-cell
lymphopoiesis
Sun Hee Kim
hematopoiesis
E2A is a transcription factor
Encodes E12 and E47: immunoglobulin enhancer-binding
proteins in B cells; bind to E box motifs in Ig promoter and
enhancer elements
Nuclear location
2 transcriptional activation domains in the NH2-terminal
1 basic helix-loop-helix (bHLH) domain in the C-terminal
E2A functions in B cell differentiation
E2A knockout mice: generate mouse embryonic stem cell lines
homozygous for E2A deletion and differentiate them in tissue
culture or subcutaneous of the mouse
E2A functions in B cell differentiation
Results: E2A -/- offspring experienced post-natal death suggesting
that E2A mutation does not affect embryonic development
E2A is not essential for muscle, cartilage, nerve, and erythroid cell
lineage formations genetic redundancy (E2-2/HEB)
E2A functions in B cell differentiation
B cell differentiation is
blocked at its earliest stage
in E2A -/-, while T cell,
macrophage, granulocyte,
and erythroid lineages
seem normal
E2A +/- heterozygotes
have about half as many B
cells
E2A-PBX1: oncogenic fusion protein
The t(1;19) fusion event combines the activation domains of
E2A with the DNA binding homeodomain region of another
protein: PBX1
E2A-PBX1: oncogenic fusion protein
E2A-PBX1 activates
expression of HOX/PBX1
target genes
PBX1 inhibits activity of
HOX proteins
HOX genes are oncogenic
when over-expressed or
become part of chimeras
containing activation
domains
E2A-PBX1: oncogenic fusion protein
E2A-PBX1 binds to a subset of the sites bound by PBX1; it is
limited and cannot bind to everything that PBX1 is able to
bind to
E2A-PBX1: oncogenic fusion protein
Deregulated association of
E2A activation domains
(with cofactors) promotes
uncontrolled cell division
Acute Lymphoblastic Leukemia (ALL)
Leukemia is cancer of the white blood cells; overproliferation of
immature white blood cells
Chromosomal translocation t(1;19) is detected in approximately
23% of all pediatric pre-B cell ALL cases
ALL is most common in childhood (4-5 years old); childhood ALL
has a better survival rate than adult ALL
ALL crowds out the normal cells in bone marrow and spreads to
other organs
Acute Lymphoblastic Leukemia (ALL)
‘Acute’ refers to the undifferentiated/immature state of circulating
lymphocytes (‘blasts’) and the rapid progression of the disease (fatal
in weeks to months if untreated)
Symptoms include weakness, fatigue, anemia, frequent infections,
weight loss, bruising, breathlessness
Diagnosed by a high white blood cell count and blasts cells seen on
blood smear, and a bone marrow biopsy
Treatment: chemotherapy/radiation therapy
References
Aspland, S. E., H. H. Bendall, and C. Murre. “The Role of
E2A-PBX1 in leukemogenesis.” Oncogene, Vol. 20, 57085717. Nature Publishing Group; 2001.
Zhuang,Y., P. Soriano, and H. Wintraub. “The Helix-LoopHelix Gene E2A Is Required for B Cell Formation.” Cell, Vol.
79, 875-884. Cell Press; 1994.
http://atlasgeneticsoncology.org/genes/e2a.html
http://www.ihop-net.org/unipub/iHOP/gs/125393.html
http://pubmed.com/w/index.php?title=Acute_lymphoblas
tic_leukemia/printable&=yes....html