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Mol. Cell. Biol., 01 1995, 517-523, Vol 15, No. 1
Y Tanuma, H Nakabayashi, M Esumi and H Endo
Transfection experiments with constructs containing various 5'-deleted
fragments of the human lipoprotein lipase (LPL) promoter and the
chloramphenicol acetyltransferase reporter gene revealed an LPL silencer
element (LSE) in the region of nucleotides -225 to -81 of the LPL gene that
functioned in Chinese hamster ovary (CHO) and HeLa cells. Gel retardation
competition analysis showed the presence of a nuclear factor(s) capable of
binding to the sequence of nucleotides -169 to - 152 of LSE (LSE-6) in a
single-stranded (opposite-strand) and double- stranded specific fashion,
the binding affinity being almost the same in the two binding forms.
Site-directed mutagenesis indicated that almost the entire sequence of
LSE-6 was necessary to form the complexes and also critical for silencing
activity in CHO cells. The amounts of this binding factor(s) in CHO and
HeLa cells were closely associated with transcriptional silencing activity.
Photochemical cross-linking experiments indicated that the single- and
double-stranded elements recognized the same binding factor(s) with
molecular masses of 54 to 63 kDa and 109 to 124 kDa. The 109- to 124-kDa
DNA binding factor(s) was found to be a doublet of that of the 54- to
63-kDa factor by isoelectric focusing or by increasing the time of exposure
to UV irradiation. When inserted upstream of another gene such as that of
the simian virus 40 enhancer/promoter of pSV2CAT, the sequence of
nucleotides -190 to -143 (LSE-1) also suppressed transcription of the
reporter gene in CHO cells. These results strongly suggest that the LSE
plays a role in regulation of LPL gene expression by suppressing its
transcription.
Copyright © 1995, American Society for Microbiology
A silencer element for the lipoprotein lipase gene promoter and cognate double- and single-stranded DNA-binding proteins
Medical Research Institute, Nihon University School of Medicine, Tokyo, Japan.
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