Cooperative DNA binding of the human HoxB5 (Hox-2.1) protein is under redox regulation in vitro.

AUTOR(ES)

Galang, C K

RESUMO

The human HoxB5 (Hox-2.1) gene product is a sequence-specific DNA binding protein. Cooperative interactions stabilize in vitro DNA binding of the HoxB5 protein to tandem binding sites by at least 100-fold relative to binding to a single site. The HoxB5 homeodomain is sufficient for sequence-specific DNA binding but not for cooperative DNA binding. Here we report that the additional protein sequence required for cooperativity is a small domain adjacent to the homeodomain on the amino-terminal side. We further show that cooperative DNA binding is under redox regulation. The HoxB5 protein binds to DNA in vitro both when oxidized or reduced but binds cooperatively only when oxidized. Mutational analysis has revealed that the cysteine residue in the turn between homeodomain helices 2 and 3 is necessary for cooperative binding and redox regulation. The enhanced DNA binding of oxidized HoxB5 protein is the opposite of the redox regulation reported for other mammalian transcription factors such as Fos, Jun, USF, NF-kappa B, c-Myb, and v-Rel, in which oxidation of cysteine residues inhibits DNA binding. Thus, specific oxidation of nuclear proteins is a potential regulatory mechanism that can act to either decrease or increase their DNA binding activity.

Documentos Relacionados

• HoxB5 Is an Upstream Transcriptional Switch for Differentiation of the Vascular Endothelium from Precursor Cells
• Conserved cysteine residue in the DNA-binding domain of the bovine papillomavirus type 1 E2 protein confers redox regulation of the DNA-binding activity in vitro.
• Vertebrate HoxB gene expression requires DNA replication
• The hexapeptide LFPWMR in Hoxb-8 is required for cooperative DNA binding with Pbx1 and Pbx2 proteins.
• HOXB5 expression in oral squamous cell carcinoma