Interactions between an HMG-1 protein and members of the Rel family

Interactions between an HMG-1 protein and members of the Rel family

Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138

Contributed by Mark Ptashne

Abstract

We show that the Drosophila protein DSP1, an HMG-1/2-like protein, binds DNA highly cooperatively with three members of the Rel family of transcriptional regulators (NF-κB, the p50 subunit of NF-κB, and the Rel domain of Dorsal). This cooperativity is apparent with DNA molecules bearing consensus Rel-protein-binding sites and is unaffected by the presence of a negative regulatory element, a sequence previously proposed to be important for mediating repression by these Rel proteins. The cooperativity observed in these DNA-binding assays is paralleled by interactions between protein pairs in the absence of DNA. We also show that in HeLa cells, as assayed by transient transfection, expression of DSP1 increases activation by Dorsal from the twist promoter and inhibits that activation from the zen promoter, consistent with the previously proposed idea that DSP1 can affect the action of Dorsal in a promoter-specific fashion.

Footnotes

↵ * Present address: National Institute for Medical Research, Division of Mammalian Development, The Ridgeway, Mill Hill, London, NW7 1AA, United Kingdom.
↵ † Present address: Département de Biologie, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada.
↵ ‡ Present address: Sloan–Kettering Molecular Biology Program, Memorial Sloan–Kettering Cancer Center, 1275 York Avenue, Box 97, New York, NY 10021.
↵ § To whom reprint requests should be addressed. E-mail: m-ptashne{at}ski.mskcc.org.
ABBREVIATIONS:

VRE,

ventral repression element;

VAR,

ventral activation response element;

NRE,

negative regulatory element;

GST,

glutathione S-transferase;

EMSA,

electrophoretic mobility-shift assay;

CAT,

chloramphenicol acetyltransferase