S Phase-specific DNA-binding proteins interacting with the Hex and Oct motifs in type I element of the wheat histone H3 promoter

The type I element (CCACGTCANCGATCCGCG) consisting of the Hex motif (CCACGT CA) and the reverse-oriented Oct motif (GATCCGCG), is necessary and suffici ent to confer the S phase-specific transcription of the wheat histone H3 (T H012) gene. The transcriptional regulation via the type I element is though t to occur through interactions between transcription factors which bind sp ecifically to the Hex and Oct motifs. Here we report S phase-specific DNA-b inding proteins interacting with the type I element in partially synchroniz ed wheat cultured cells. Hex motif-binding proteins found here resembled HB P-1a, as reported previously in terms of DNA-binding specificity. DNA-bindi ng activities of the HBP-1a-like proteins were modulated by phosphorylation /dephosphorylation. In the electrophoretic mobility shift assay of the whea t nuclear extract, we also found three Oct motif-specific binding proteins, named OBRF (octamer-binding regulatory factor)-1, -2 and -3. One of the HB P-1a-like proteins and OBRF-1 appeared predominantly at the S phase. Thus, it was supposed that these two factors play a crucial role in the S phase-s pecific regulation of wheat histone gene expression. (C) 2000 Elsevier Scie nce B.V. All rights reserved.