CHARACTERIZATION AND EXPRESSION OF A RICE RAD23 GENE

In order to identify proteins that interact with plant transcriptional complexes, we performed a two-hybrid screen in yeast using a cDNA lib rary from embryogenic rice suspension cultures and the plant transcrip tional activator viviparous-1 (vp1) as 'bait'. In this screen, we dete cted an interaction between VP1 and a rice homologue of the Saccharomy ces cerevisiae RAD23 gene (osRAD23). The RAD23 protein is associated w ith the general transcriptional machinery in yeast, and is believed to play a role in the processes of nucleotide excision repair in yeast a nd mammalian cells. This report is the first identification of a RAD23 homolog in plants. The osRAD23 amino acid sequence shares 50-60% simi larity throughout its length with RAD23 sequences from yeast, mice, an d man. osRAD23 contains a characteristic ubiquitin-like domain at its N-terminus, which is similar to other RAD23 genes. Analysis of the exp ressed sequence tag database identifies two different classes of RAD23 genes in both Arabidopsis and rice. Southern analysis of rice genomic DNA indicated the presence of at least two RAD23-like genes. A single transcript (1.5 kb) of osRAD23 was detected in total RNA from rice em bryonic tissue, while three transcripts (1.8, 1.5 and 1.0 kb) were obs erved in total RNA from vegetative tissues of rice.