Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Proc Natl Acad Sci U S A. 1991 Jul 1;88(13):5670-4.

DNA looping and Sp1 multimer links: a mechanism for transcriptional synergism and enhancement.

Author information

  • 1Biology Department, Brookhaven National Laboratory, Upton, NY 11973.

Abstract

Using conventional and scanning transmission electron microscopy, we have examined the physical basis of long-range enhancer effects between distal and proximal elements in a eukaryotic promoter. Specifically, we have studied binding of human transcription factor Sp1 to 10-base-pair G+C-rich elements ("GC boxes") located at -100 and +1700 relative to the RNA start site. It was previously observed that the distantly located site functions in synergism with the promoter-proximal site to strongly activate transcription in vivo. Here we demonstrate that this synergism is likely to be a direct consequence of interactions between remote and local Sp1, the remote Sp1 translocated to the promoter by a DNA loop. Scanning transmission electron microscopy shows that Sp1 initially forms a tetramer and subsequently assembles multiple tetramers stacked in register at the DNA loop juncture. This unexpected finding not only provides the physical basis for loop formation but also defines a biological process leading to strongly increased concentration of activator protein at the promoter. The mechanism may unify the problem of transcriptional activation by removing enhancer action as a separate class of regulatory activity.

PMID:
2062845
[PubMed - indexed for MEDLINE]
PMCID:
PMC51939
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk