CHROMATIN COMPONENTS AS PART OF A PUTATIVE TRANSCRIPTIONAL REPRESSINGCOMPLEX

The Drosophila HMG1-like protein DSP1 Has identified by its ability to inhibit the transcriptional activating function of Dorsal in a promot er-specific fashion in yeast, We show here that DSP1 as Hell as its ma mmalian homolog hHMG2 bind to the mammalian protein SP100B and that SP 100B in turn binds to human homologs of HP1, The latter is a Drosophil a protein that is inolved in transcriptional silencing. Each of these proteins represses transcription when tethered to DNA in mammalian cel ls. These results suggest how heterochromatin proteins might be recrui ted to specific sites on DNA with resultant specific effects on gene e xpression.