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Multiple protein-binding sites in an intracisternal A particle long terminal repeat
1Laboratory of Biochemistry, National Cancer Institute, Bethesda, Maryland 20892.
Journal of Virology
|November 1, 1988
Summary
Intracisternal A particle (IAP) long terminal repeats (LTRs) contain multiple protein-binding sites that regulate transcription. Nuclear factors binding to these sites vary in amount and affinity across different cell types, suggesting complex transcriptional control.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Long terminal repeats (LTRs) of intracisternal A particles (IAPs) act as promoters.
- IAP LTRs respond to transcriptional factors induced by nuclear oncogene products.
Purpose of the Study:
- To investigate the protein-binding sites within the U3 region of a mouse IAP LTR.
- To characterize the nuclear factors that interact with the IAP LTR and their regulation by oncogenes.
Main Methods:
- Exonuclease III footprinting to identify protein-binding sites.
- DNase I footprinting to map distinct protein-binding domains.
- Gel retardation assays with oligonucleotide probes to analyze nuclear factor binding.
Main Results:
- Identified multiple protein-binding sites within the IAP LTR U3 region.
- Demonstrated varying amounts and affinities of nuclear factors across different cell lines, including those with oncogenes.
- Discovered at least five distinct protein-binding domains, some homologous to known enhancer and transcription factor binding sites (SV40 core enhancer, SP1, AP-1).
Conclusions:
- The IAP LTR possesses a complex regulatory mechanism involving multiple, closely spaced protein-binding sites.
- Nuclear factor binding to IAP LTRs is modulated by cellular transformation and oncogene expression.
- These findings highlight intricate transcriptional regulation of IAP elements.
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