The complete nucleotide sequence of the tobacco chloroplast genome: its gene organization and expression.

The complete nucleotide sequence (155 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA has been determined. It contains two copies of an identical 25 339 bp inverted repeat, which are separated by a 86 684 bp and a 18 482 bp single-copy region. The genes for 4 different rRNAs, 30 different tRNAs, 39 different proteins and 11 other predicted protein coding genes have been located. Among them, 15 genes contain introns. Blot hybridization revealed that all rRNA and tRNA genes and 27 protein genes so far analysed are transcribed in the chloroplast and that primary transcripts of the split genes hitherto examined are spliced. Five sequences coding for proteins homologous to components of the respiratory-chain NADH dehydrogenase from human mitochondria have been found. The 30 tRNAs predicted from their genes are sufficient to read all codons if the ;two out of three' and ;U:N wobble' mechanisms operate in the chloroplast. Two sequences which autonomously replicate in yeast have also been mapped. The sequence and expression analyses indicate both prokaryotic and eukaryotic features of the chloroplast genes.

Hippocampal cholinergic neurostimulating peptides (HCNP).

Neuronal development and differentiation require a variety of cell interactions. Diffusible molecules from target neurons play an important part in mediating such interactions. Our early studies used explant culture technique to examine the factors that enhance the differentiation of septo-hippocampal cholinergic neurons, and they revealed that several components resident in the hippocampus are involved in the differentiation of presynaptic cholinergic neurons in the medial septal nucleus. One of these components, originally purified from young rat hippocampus, is a novel undecapeptide (hippocampal cholinergic neurostimulating peptide; HCNP); this enhances the production of ChAT, but not of AchE. Later experiments revealed that: (1) a specific receptor appears to mediate this effect; (2) NGF and HCNP act cooperatively to regulate cholinergic phenotype development in the medial septal nucleus in culture; and (3) these two molecules differ both in their mechanism of release from the hippocampus and their mechanism of action on cholinergic neurons. The amino acid sequence deduced from base sequence analysis of cloned HCNP-precursor protein cDNA shows that HCNP is located at the N-terminal domain of its precursor protein. The 21 kDa HCNP precursor protein shows homology with other proteins, and it functions not only as an HCNP precursor, but also as a binding protein for ATP, opioids and phosphatidylethanolamine. The distribution and localization of HCNP-related components and the expression of their mRNAs support the notion that the precursor protein is multifunctional. In keeping with its multiple functions, the multiple enhancers and promoters found in the genomic DNA for HCNP precursor protein may be involved in the regulation of its gene in a variety of cells and at different stages of development. Furthermore, several lines of evidence obtained from studies of humans and animal models suggest that certain types of memory and learning disorders are associated with abnormal accumulation and expression of HCNP analogue peptide and/or its precursor protein mRNA in the hippocampus.

The complete nucleotide sequence of 16S ribosomal RNA gene from tobacco chloroplasts.

The complete nucleotide sequence of 16S ribosomal RNA gene from tobacco chloroplasts has been determined. This nucleotide sequence has 96% homology with that of maize chloroplast 16S rRNA gene and 74% homology with that of Escherichia coli 16S gene. The 3' terminal region of this gene contains the sequence ACCTCC which is complementary to sequences found at the 5' termini of prokaryotic mRNAs. The large stem and loop structure can be constructed from the sequences surrounding the 5' and 3' ends of the 16S gene. These observation demonstrate the prokaryotic nature of chloroplast 16S rRNA.

Sequence homology of rat and human HCNP precursor proteins, bovine phosphatidylethanolamine-binding protein and rat 23-kDa protein associated with the opioid-binding protein.

The hippocampal cholinergic neurostimulating peptide (HCNP) enhances acetylcholine synthesis in rat medial septal tissues. We have cloned the cDNAs of the precursor proteins of rat and human HCNP and deduced their respective amino acid sequences. The HCNP sequences aligned at the N-terminal regions of their precursors. The deduced amino acid sequences showed homology with those of the bovine brain phosphatidylethanolamine-binding protein and the rat protein associated with the opioid-binding protein. These observations suggest that the HCNP precursor proteins may have multiple functions.

Mechanism of expression of the rat HCNP precursor protein gene.

The hippocampal cholinergic neurostimulating peptide (HCNP), isolated from hippocampal tissue of 10- to 12-day-old rats, enhances the in vitro synthesis of acetylcholine in medial septal tissue explants. The HCNP precursor is a 21 kDa protein that binds hydrophobic ligands and Mg-ATP, and is associated with the opioid-binding protein. We employed an HCNP-precursor cDNA as probe to clone the genomic DNA, used for mapping of the exon-intron structure of the gene. We also determined the nucleotide structure of the promoter region of the rat HCNP precursor protein gene. By using S1 mapping and CAT as a reporter, we found multiple promoters that were aligned in the 5' untranslated region. In addition, the presence of several putative enhancer binding sequences were tested by electrophoresis mobility shift assays. Northern blot analysis revealed that the gene is expressed in a variety of rat tissues and various subregions of the brain. These results suggest that HCNP-precursor gene expression is regulated by a general transactivation factor such as SP1, and that the specific presence of the bioactive HCNP in certain tissues results from post-translational events such as proteolytic processing of the precursor protein, which takes place predominantly in the hippocampus of young rats.

Demonstration of deacetylated hippocampal cholinergic neurostimulating peptide and its precursor protein in rat tissues.

This report concerns the demonstration of hippocampal cholinergic neurostimulating peptide (HCNP), its deacetylated analogue (free HCNP) and HCNP precursor protein in rat tissues. To avoid possible enzymatic degradation during sample manipulation, tissue extracts were prepared under acidic conditions using trifluoroacetic acid. The tissue contents of free HCNP and of precursor protein were determined by radioimmuno-assay (RIA) using two antibodies with different specificities, and by a combination of HPLC and RIA. Free HCNP was detected in neuronal and renal tissues, but not in liver. All tissues examined had measurable amounts of HCNP precursor protein. The concentrations of free HCNP and precursor in neuronal tissues were inversely related to the age. These results suggest that the deacetylated analogue of HCNP and its precursor protein may have significant physiological functions, especially in the central nervous system of young animals.

Neuronal expression of hippocampal cholinergic neurostimulating peptide (HCNP)-precursor mRNA in rat brain.

The expression of hippocampal cholinergic neurostimulating peptide (HCNP)-precursor mRNA in rat brain was examined by Northern blot and in situ hybridization analyses. Northern blot analysis using rat HCNP-precursor cDNA revealed a 1.1-kilobase (kb) transcript. A message of identical size was also detected with the antisense precursor riboprobe. In situ hybridization disclosed that HCNP-precursor mRNA was expressed in many areas of the brain, including the basal forebrain cholinergic system, the olfactory system, and the cerebellum. Very high levels were seen in the pyramidal cells of the CA3 region and in the hilus of the dentate gyrus of the hippocampal formation. High levels were also found in the septal area, piriform cortex, entorhinal cortex, thalamic nuclei, subthalamic nuclei, medial habenular nuclei, substantia nigra, Purkinje cells of the cerebellum, and choroid plexus. By contrast, glial cells were not labeled by the antisense HCNP-precursor riboprobe. The expression of HCNP-precursor mRNA by a variety of neurons suggests that HCNP and its precursor protein play significant roles in the stimulation of cholinergic activity, as well as in other not yet defined functions.

Sequence of a putative promoter region for the rRNA genes of tobacco chloroplast DNA.

The nucleotide sequence of the segment of tobacco chloroplast DNA adjacent to and including the start of the 16S rRNA gene has been determined. The region just preceding this gene was found to contain a tRNAVal gene and promoter-type sequences similar to those which occur in E. coli were found before this tRNA gene. E. coli RNA polymerase can recognize these sequences and in vitro co-transcribes the tRNA and rRNA genes.

The distribution and properties of RNA primed initiation sites of DNA synthesis at the replication origin of Escherichia coli chromosome.

RNA-linked DNA molecules were obtained from E. coli dnaCts cells synchronously initiating a new round of chromosome replication. The deoxynucleotides at the transition from primer RNA to DNA were 32P-labeled, and their positions were located on the nucleotide sequence of 1.4 kb genomic region (position -906 to +493) including the oriC and its leftside flanking region. In the r-strand (the counterclockwise strand), many strong transition sites were mapped in the left half portion of the oriC and a few weak sites in the left outside region. In the 1-strand (the clockwise strand), no transition sites were found inside the oriC but many weak sites were found in the left outside region. The results support the initiation mechanism in which the first leading strand synthesis starts with the r-strand counterclockwise from the oriC that is followed by the 1-strand synthesis on the displaced template strand on the left of oriC. Primer RNA molecules attached to the strong r-strand transition sites were only a few residues in length. Properties of the transition sites were discussed.