Repression of histone H5 gene expression in chicken mature erythrocytes is correlated with reduced DNA-binding activities of transcription factors Sp1 and GATA-1.

During the final stages of erythroid maturation, the expression of the chicken histone H5 gene ceases. The histone H5 promoter has binding sites for Sp1 and UPE-binding protein. The 3' histone H5 enhancer has binding sites for Sp1, GATA-1 and NF1. Here, we show that the DNA-binding activities of transcription factors Sp1 and GATA-1 is reduced 5- to 10-fold in mature cells, while the activities of UPE-binding protein and NF1 remain the same in mature and immature erythrocytes. The reduced activities of Sp1 and GATA-1 may contribute to the inactivation of the histone H5 gene in mature erythrocytes.