RESUMO
We previously described the preparation of a protein fraction that bound to the promoter region of the rRNA gene of Vicia faba. We now describe two additional protein fractions that interact with this DNA element. The three protein fractions have similar binding properties with the exception of their binding stabilities. DNase I footprinting experiments revealed that these protein fractions bind to a region that is located about 60 bp upstream from the site of initiation of transcription. From methylation interference experiments and gel-retardation assays with mutated oligonucleotides, it was evident that the protein fractions required the same residues for the formation of stable DNA-protein(s) complexes. However, the three protein fractions were chromatographically distinguishable and the stability of their binding to DNA was different. Although the functions of these fractions are still unknown, the fact that several protein fractions can bind to a narrow region near the site of initiation of transcription is of considerable interest in terms of the mechanism of transcription of the rRNA gene.
Assuntos
Fabaceae/genética , Proteínas de Plantas/metabolismo , Plantas Medicinais , Regiões Promotoras Genéticas , RNA Ribossômico/genética , Proteínas de Ligação a RNA/metabolismo , Sequência de Bases , Núcleo Celular/metabolismo , DNA de Plantas , Dados de Sequência Molecular , Ligação Proteica , RNA Ribossômico/metabolismoRESUMO
Three genes and one mutant gene for tRNA(Phe) (GAA) and one gene for tRNA(Ala) (UGC) were isolated from a whole-cell DNA library of Arabidopsis thaliana. All three tRNA(Phe) genes are identical in their nucleotide sequence, but differ in their 5' and 3' flanking regions. The mutant tRNA(Phe) (GAA) gene differs from the other three genes by one nucleotide change from highly conserved G to C at the 57th nucleotide position. The primary structure of the first tRNA(Ala) gene was also determined in this experiment.
Assuntos
Genes de Plantas , Plantas/genética , RNA de Transferência de Alanina/genética , RNA de Transferência de Fenilalanina/genética , Sequência de Bases , Núcleo Celular , Fabaceae/genética , Biblioteca Genômica , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Plantas Medicinais , Homologia de Sequência do Ácido Nucleico , Especificidade da EspécieRESUMO
The complete nucleotide sequence of the rDNA large spacer region was determined for two related legume plants, Vicia faba and Pisum sativum. In the large spacers of both plants, there were one or several tandem arrays of repeated sequences which account well for the length heterogeneity of the rDNA repeating units. When the entire lengths of Vicia and Pisum rDNA large spacers were compared, significant sequence similarity ranging from approximately 50 to 80% was observed, thus a close phylogenetical relationship was revealed. However, organization patterns of these rDNA spacers were clearly different from each other. The Pisum rDNA large spacer contained only one type of repeated sequence of about 175 bp, whereas the Vicia contained five kinds of repeated sequence. In addition, the initiation site for transcription was tentatively determined by S1 protection experiment.
Assuntos
DNA Ribossômico/genética , Plantas/genética , Sequência de Bases , DNA Ribossômico/química , Fabaceae/genética , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , Plantas Medicinais , Precursores de RNA/genética , Sequências Repetitivas de Ácido Nucleico , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie , Transcrição GênicaRESUMO
Nucleotide sequences of the first and second internal transcribed spacers (ITS1 and ITS2, respectively) of ribosomal DNA (rDNA) from two dicot plants, carrot and broad bean, were determined. These sequences were compared with those of rice, a monocot plant, and other eukaryotic organisms. Both types of ITS region in some species of Angiospermae were the shortest among all eukaryotes so far examined and showed a wide range of variation in their G+C content, in contrast to a general trend toward very high G+C content in animals. Phylogenetic relationships of plants with animals and lower eukaryotes were considered using the nucleotide sequences of carrot and broad bean 5.8S rDNA that were determined in the present study, together with that of wheat 5.8S rRNA, which has been reported previously.