Structure and expression of the tobacco nuclear gene encoding RNA-binding protein RZ-1: the existence of an intron in the 3'-untranslated region.

We have previously characterized a tobacco cDNA encoding a novel type RNA-binding protein (RZ-1), which contains a zinc finger motif in addition to a consensus sequence-type RNA-binding domain and is localized in the nucleus. Here we isolated its genomic clone from a Nicotiana sylvestris genomic library. Southern blot analysis suggested that RZ-1 is coded for by a single locus per haploid genome. Comparison of the cDNA and genomic sequences indicated that the RZ-1 gene contains two introns, one in the coding region and another in the 3'-untranslated region. RT-PCR and ribonuclease protection analyses showed that splicing of RZ-1 pre-mRNA occurs efficiently. The RZ-1 protein is actively synthesized in rapidly dividing tobacco cells, as demonstrated by immunoblot analysis.