Isolation, partial purification and differential DNA-binding properties of putative high-mobility-group proteins from rice

Abstract

Putative high-mobility-group (HMG) proteins were isolated from 10-11- day-old rice (Oryza sativa L. cv. IR36) shoots and roots, and from ungerminated rice grains. Nine proteins below 30 kDa which fulfilled the criteria for HMG proteins were identified from rice shoots and subjected to reversed-phase perfusion chromatography as an initial purification step. Southwestern hybridisation analysis established novel selective and differential binding of individual pea, wheat and rice HMG proteins to A/T- and G/C-rich DNA probes. Gel retardation assays using sequences derived from the pea plastocyanin and oat phytochrome A3 gene promoters have suggested that rice shoot HMG protein extracts contain a DNA-binding protein factor resembling PCF1 from pea in its binding characteristics, and that this factor is closely related to the HMG-I/Y-like PFI protein from rice. An analysis of fractionated rice shoot HMG proteins suggests that specific promoter-binding activity resides in the 26 kDa HMGα protein.