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Mol. Cell. Biol., 03 1995, 1513-1521, Vol 15, No. 3
S Saisanit and XH Sun
The helix-loop-helix (HLH) Id proteins have been reported to function as
inhibitors of various differentiation programs. The HLH motif mediates
dimer formation between Id and the basic HLH transcription factors. Since
Id proteins lack the basic region responsible for DNA binding, the
heterodimers cannot bind to DNA. Id proteins have also been found to be
involved in early B-cell differentiation. They are expressed at high levels
in progenitor B cells (pro-B cells), and the expression is diminished in
pre-B cells and mature B cells. This expression pattern correlates
inversely with basic HLH protein activity and immunoglobulin enhancer
function in B-cell development. Regulation of Id expression may play an
important role in transcriptional control of immunoglobulin genes and
therefore in B-cell differentiation. We have characterized the regulatory
elements of the Id1 gene. Using stable transfectants, transient
transfection, and mobility shift assays, we have identified an 8-bp element
designated PBE (pro-B enhancer) downstream of the Id1 gene that is
responsible for a pro-B- cell-specific enhancer activity. A
pro-B-cell-specific protein complex was found to bind to the 8-bp PBE
element. Substitution mutagenesis at this binding site showed that it is
indeed of functional importance in regulating the pro-B-cell-specific
expression of the Id1 gene.
Copyright © 1995, American Society for Microbiology
A novel enhancer, the pro-B enhancer, regulates Id1 gene expression in progenitor B cells
Department of Cell Biology, New York University Medical Center, New York 10016.
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