Biomedical Engineering Reference
In-Depth Information
Tabl e 2. 5.
Subclass-B basic helix-loop-helix proteins that belong to E/E2A protein and inhibitor
of DNA binding (ID) families. Transcription factors of the E protein family can heterodimerize
with subclass-A basic helix-loop-helix protein bHLHa17 (a.k.a. T-cell acute lymphocytic leuke-
mia protein-1 [TAL1] and stem cell leukemia factor [SCL]) and bHLHa18 (a.k.a. lymphoblastic
leukemia-derived sequence-1 [LyL1]).
bHLHb type
Main alias
Other aliases
E2A transcription factors
bHLHb19
TcF4
E2-2, TcF7L2, ITF2, SEF2
bHLHb20
TcF12
HEB, HTF4
bHLHb21
TcFE2
α
/TcF3
E2A, ITF1
bHLHb21
E12
TcFE2a
E12
bHLHb21
E47
TcF3
E47
E protein partners (heterodimers)
bHLHa17
TAL1
SCL, TCL5
bHLHa18
LyL1
Inhibitors of DNA binding
bHLHb24
ID1
bHLHb25
ID3
bHLHb26
ID2
bHLHb27
ID4
The regulation of most GATA1-dependent genes requires the tethering to ZFPM1
protein that is restricted to erythroid cells and megakaryocytes. Cofactor ZFPM1
that operates as both an activator and repressor binds to the nucleosome remodeling
and deacetylase (NuRD) complex that can also be detected at both inhibited and
active GATA1-ZFPM1 target genes [
67
]. Consequently, the NuRD complex is a
versatile cofactor for transcription factors that activate and repress gene transcription
according to lineage-specific gene expression patterns.
2.4.1.2
Transcription Factors of Self-Renewal of Hematopoietic
Stem Cells
Homeobox Gene Family
Self-renewal of hematopoietic stem cells is associated with the homeobox (HOX)
gene family (Table
2.6
), especially transcription factors HoxA9 and HoxB4 that
cause an expansion of cultured hematopoietic stem cell populations. Homeobox
gene products are homeodomain-containing proteins with tissue-specific functions
that bind to DNA enhancer sequences, acting as both a repressor at given genes
and activator at others. The DNA-binding homeodomain is a highly conserved 60
amino acid-long motif. Homeobox gene products regulate the proper placement of
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