Identification of a Brassica napus cDNA clone encoding a peptide highly related to ABC10 beta, the smallest and common subunit of RNA polymerases of Saccharomyces cerevisiae

Abstract

Nuclear RNA polymerases, fundamental components of eukaryotic cells, are multisubunit enzymes. While the structure and function of the RNA polymerase subunits have been extensively studied in yeast and mammals, those of plant RNA polymerase subunits are largely unknown. Here we report the identification of a Brassica napus cDNA clone (pBRP10 beta) encoding a peptide (BRP10 beta) highly related to ABC10 beta, a 70 amino acid peptide that is the smallest and common subunit of the three yeast RNA polymerases and is essential for yeast cell viability. The deduced open reading frame of the clone is 216 bp long, encoding a 71-amino acid peptide. The deduced peptide shows 78% similarity to the yeast ABC10 beta and shows high similarities to other eukaryotic ABC10 beta homologs as well. In addition, it contains a potential zinc-binding motif conserved in ABC10 beta homologs as well as in other subunits of RNA polymerases. Genomic DNA blot analysis suggests that this gene may constitute a gene family in B. napus. RNA gel blot a nalysis shows that a single band of transcript is detected in all major organs. Our finding suggests that the RNA polymerases of B. napus may contain a peptide subunit similar to the yeast ABC10 beta subunit.