IDENTIFICATION OF YY1 SEQUENCES NECESSARY FOR ASSOCIATION WITH THE NUCLEAR MATRIX AND FOR TRANSCRIPTIONAL REPRESSION FUNCTIONS

YY1 is a zinc finger-containing transcription factor that can both rep ress and activate transcription. YY1 appears to use multiple mechanism s to carry out its diverse functions. Recently, it was observed that Y Y1 can exist in multiple nuclear compartments. In addition to being pr esent in the nuclear extract fraction, YY1 is also a component of the nuclear matrix. We show that YY1 can be sequestered in vivo into a hig h-molecular-weight complex and can be dislodged from this complex eith er by treatment with formamide or by incubation with an oligonucleotid e containing the YY1 DNA binding site sequence. By transfecting plasmi ds expressing various YY1 deletion constructs and subsequent nuclear f ractionation, we have identified sequences necessary for association w ith the nuclear matrix. These sequences (residues 256-340) co-localize d with those necessary for in vivo sequestration of YY1 into the high- molecular-weight complex. We have also characterized YY1 sequences nec essary for repression of activated transcription (residues 333-371) an d those necessary for masking of the YY1 transactivation domain (resid ues 371-397). Sequences that repress activated transcription partially overlap YY1 sequences necessary for association with the nuclear matr ix. However, these sequences are distinct from those that appear to ma sk the YY1 transactivation domain. The potential role of nuclear matri x association in controlling YY1 function is discussed. (C) 1998 Wiley -Liss, Inc.