Figure 5

A model is suggested for the reduction of β-galactosidase gene expression in the presence of a poly pur.pyr sequence. Before transcription initiation, nucleosome disruption is necessary from DNA sequences by the Gal4-Gal80 complex. This protein complex may not disrupt the nucleosome from the single copy and tandemly repeated multiple copy poly pur.pyr sequence due to the higher affinity of binding with the nucleosome while these may disrupt nucleosomes from normal duplex carrying sequences and from the inverted orientation of the poly pur.pyr sequence. It is possible that the single and tandem multiple copy of the poly pur.pyr sequence may form an intramolecular triplex while inverted orientation disrupts the structure.