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We have developed a system to transcribe the yeast 5S rRNA gene in the absence of the transcription factor TFIIIA. A long transcript was synthesized both in vitro and in vivo from a hybrid gene in which the tRNA-like promoter sequence of the RPR1 gene was fused to the yeast 5S RNA gene. No internal initiation directed by the endogenous 5S rDNA promoter or any processing of the hybrid transcript was observed in vitro. Yeast cells devoid of transcription factor TFIIIA, which, therefore, could not synthesize any 5S rRNA from the endogenous chromosomal copies of 5S rDNA, could survive if they carried the hybrid RPR1-5S construct on a multicopy plasmid. In this case, the only source of 5S rRNA was the precursor RPR1-5S transcript that gave rise to two RNA species slightly larger than wild-type 5S rRNA. This establishes that the only essential function of TFIIIA is to promote the synthesis of 5S rRNA. However, cells devoid of TFIIIA and surviving with these two RNAs grew more slowly at 30[degrees]C compared with wild-type cells and were thermosensitive at 37[degrees]C.

DNA sequences of mitochondrial large and small ribosomal subunit genes help analyze the phylogeny of cockroaches, termites and mantids and compare the observed phylogeny with that proposed by Mckittrick. These studies suggest that cockroaches belong to a monophyletic group, with only limited similarity between subfamilies and genera, implying that Cryptocercus punctualatus and Mastotermes darwiniensis are not closely related. These observations concur with Mckittrick's proposals.

Investigations of the location of the tridecamer transcription termination signal seen in mammalian mtDNA indicate that this termination signal is present in equivalent sites in various organisms from protozoa to mammals. A well-conserved heptamer TGGCAGA, the mitochondrial rRNA termination box, is established. Presentation of the sequence and its location with respect to mitochondrial rRNA genes across a wide phylogenetic species indicates the importance of its role as a transcription signal in human mtDNA.

A phagotrophic amoeba has acquired the ability to photosynthesize by retaining a prey cell as an endosymbiont, and chlorarachniophytes are found to have a photosynthetic eukaryotic environment. Lateral transfer of a chloroplast through eukaryotic lineage creates a new phylum of algae. Pulsed field gel electrophoresis is used to locate chromosomes attached to endosymbiont genome.

An analysis of the Saccharomyces cerevisiae 5S rRNA genes (5S rDNA), through a simple no-background assay designed for high-resolution in vivo examination of yeast chromatin, proves that nucleosomes occupy alternative locations characterized by a distinct helical phase, and totally cover this chromosomal site. Nucleosome localization is primarily influenced by sequence intrinsic rotational signals.

The sequences of the 16S ribosomal RNA genes of Pyrobaculum aerophilum and Pb. islandicum were determined and compared. The results showed that Pb.aerophilum and Pb. islandicum are very related, with 98% similarity in their 16s rRNA genes. However, an intron within the 16S rRNA gene of Pb. aerophilum was detected. This is the first instance of an intron within the 16S rRNA gene of a prokaryote.

The chromatin structure of the ribosomal genes in tomato cells were determined. Micrococcal nuclease analysis of the ribosomal genes showed that 80% of these genes are folded in a nucleosomal structure similar to bulk inactive chromatin. Psoralen crosslinking analysis further showed that only 20% of the tomato ribosomal genes are in the active conformation. Compared to other lower eukaryotes and mice, the proportion of tomato ribosomal genes in open or closed conformations is markedly different.