Interaction of transcription factor YY1 with a replication-enhancing element, REE1, in an autonomously replicating human chromosome fragment

We have previously shown that autonomous replication of human chromosome fragments is stimulated by the presence of an 18 bp sequence, REE1, which exhibits transcriptional silencer activity. The REE1 sequence is partly homologous with the serum response element (SRE) required for expression of the human c-fosgene, Here we have examined interaction of REE1 with human nuclear proteins using a gel retardation assay. One of the REE1-protein complexes formed showed almost the same mobility as the SRE-protein complex and complex formation was competitively inhibited by the SRE fragment. The protein complex with REE1 as well as that with SRE was found to contain the transcription factor YY1, known to bind to the SRE, These results suggest that YY1 protein may participate in stimulation of replication through its interaction with REE1.