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

Putative high-mobility-group (HMG) proteins were isolated from 10-11-day-ol d rice (Oryza sativa L. cv. IR36) shoots and roots, and from ungerminated r ice 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 hybr idisation 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 pr otein extracts contain a DNA-binding protein factor resembling PCF1 from pe a in its binding characteristics, and that this factor is closely related t o the HMG-I/Y-like PF1 protein from rice. An analysis of fractionated rice shoot HMG proteins suggests that specific promoter-binding activity resides in the 26 kDa HMG alpha protein. (C) 1998 Elsevier Science Ireland Ltd. Al l rights reserved.