Chicken lysozyme is highly expressed in the oviduct. The 5' regulatory region of this gene contains a negative element that represses transcription. To assess the molecular basis underlying the regulation of lysozyme gene expression, we investigated the binding protein to this region. Sequence motif analysis suggested the existence of putative YY1 binding sites in this regulatory region. Electrophoretic mobility shift assay showed the specific binding of YY1 to the negative element. In addition, chromatin immunoprecipitation assay indicated that YY1 specifically bound to the negative element in oviduct cells but not in erythrocytes. It was suggested by electrophoretic mobility shift assay and chromatin immunoprecipitation assay that YY1 also bound to the negative regulatory region in the promoter of the ovalbumin gene which also shows oviduct-specific expression. Western blot analysis showed that YY1 was expressed in relatively high levels in the oviduct and nucleus fractionation experiments showed that YY1 was localized both in chromosome and nuclear matrix fractions. These results suggest that there are some specific roles in the negative regulatory regions of these genes in relation to the multifunctional transcription factor YY1.