Abstract
Deadenylation, a shortening of the poly(A) tail, is the first and rate-limiting step of mRNA turnover for many transcripts in eukaryotes. Identification and characterization of the functional deadenylases are, therefore, important to understand the mRNA turnover process. The complex of Carbon Catabolite Repressor 4 (Ccr4) / Ccr4-associated factor 1 (Caf1) and several associated factors have been identified as a major cytoplasmic deadenylase in yeast. Based on the genetic analyses of ccr4 and caf1 mutants, Ccr4 is reported to be a catalytic subdomain of this complex. Arabidopsis has six homologous proteins of yeast Ccr4. Among them, AtCCR4-1 and AtCCR4-2 are most similar to yeast Ccr4. Transient expression analysis using the GFP fusion of AtCCR4-1 or AtCCR4-2 indicated that both are localized in specific granule called P-body, which is the region within the cytoplasm consisting of many enzymes involved in mRNA turnover. To elucidate the function of AtCCR4-1 and AtCCR4-2 in vivo, the double mutant was constructed. The double mutant showed pleiotropic phenotypes, suggesting a possibility that AtCCR4-1 and AtCCR4-2 might be general deadenylases in Arabidopsis.
