Chromatin components as part of a putative transcriptional repressing complex

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

Contributed by Mark Ptashne

Abstract

The Drosophila HMG1-like protein DSP1 was identified by its ability to inhibit the transcriptional activating function of Dorsal in a promoter-specific fashion in yeast. We show here that DSP1 as well as its mammalian homolog hHMG2 bind to the mammalian protein SP100B and that SP100B in turn binds to human homologs of HP1. The latter is a Drosophila protein that is involved in transcriptional silencing. Each of these proteins represses transcription when tethered to DNA in mammalian cells. These results suggest how heterochromatin proteins might be recruited to specific sites on DNA with resultant specific effects on gene expression.

Footnotes

↵ § To whom reprint requests should be addressed. e-mail: m-ptashne{at}ski.mskcc.org.
↵ † Present Address: Max-Delbrück-Laboratorium in der Max-Planck-Gesellschaft, Carl-von-Linné-Weg 10, D-50829 Köln, Germany.
↵ ‡ Present Address: Nucleic Acids Biochemistry/Synthesis, Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 595, New York, NY 10021.
ABBREVIATIONS:

CD,

chromo domain;

CSD,

chromo shadow domain;

HMG,

high mobility group;

NB,

nuclear body;

rII,

GAL4 activating region II (768–881);

CAT,

chloramphenicol acetyltransferase