A role for endothelial NO synthase in LTP revealed by adenovirus-mediated inhibition and rescue.

Pharmacological studies support the idea that nitric oxide (NO) serves as a retrograde messenger during long-term potentiation (LTP) in area CA1 of the hippocampus. Mice with a defective form of the gene for neuronal NO synthase (nNOS), however, exhibit normal LTP. The myristoyl protein endothelial NOS (eNOS) is present in the dendrites of CA1 neurons. Recombinant adenovirus vectors containing either a truncated eNOS (a putative dominant negative) or an eNOS fused to a transmembrane protein were used to demonstrate that membrane-targeted eNOS is required for LTP. The membrane localization of eNOS may optimally position the enzyme both to respond to Ca2+ influx and to release NO into the extracellular space during LTP induction.

Structure of the two related elastase genes expressed in the rat pancreas.

We have isolated and characterized rat genomic DNA fragments bearing the two secretory elastase genes that are expressed in the exocrine pancreas. The complete exonic sequences for each of the genes as well as considerable intronic and flanking sequences are reported. Each elastase gene is interrupted by seven intervening sequences which are located at corresponding positions within the two genes, with one exception: the third intron of the elastase II gene has shifted one codon in the 5' direction. The placement of introns within the amino acid coding domains in part may reflect the formation of the progenitor serine protease gene by the duplication of an exon encoding a characteristic polypeptide structure comprising three beta sheets. The activation peptides of the zymogens and the signal peptides, which form discrete functional domains in the protein precursors, are encoded by separate exons. In addition to the TATAA box, the two genes share considerable sequence similarity in the 5'-proximal flanking regions (up to approximately 450 base pairs upstream); however, a number of gaps must be introduced to optimize the sequence alignment. The similarities are largely confined to six oligonucleotide regions with greater than 70% sequence conservation. The elastase I gene has a perfect repeating copolymer (GT)24 located 427-379 nucleotides upstream from the start of transcription. The elastase II gene has a similar GT-rich region (52/55 G or T) located 384-330 nucleotides upstream. Comparison of the 5'-flanking regions of the two elastase genes with those of pancreatic chymotrypsin and trypsin I and II reveals that one of the six conserved oligonucleotide regions is generally conserved for these genes as well. This conserved region contains putative enhancer core sequences.

Rat pancreatic ribonuclease messenger RNA. The nucleotide sequence of the entire mRNA and the derived amino acid sequence of the pre-enzyme.

We have cloned via recombinant DNA technology the mRNA sequence of rat pancreatic ribonuclease, and have determined the entire nucleotide sequence of the mature message. Clones bearing RNase sequences within a double-stranded complementary DNA library of rat pancreatic mRNA were initially detected by hybridization with size-fractionated rat pancreatic polyadenylated RNA that included mRNA 0.85 to 1.0 kilobase in length. Recombinant plasmids bearing RNase mRNA sequences were conclusively identified by comparison of the amino acid sequence of the encoded protein with the known amino acid sequence of rat RNase. RNase mRNA is 783 nucleotides in length, plus a poly(a) tail with an average length of 140 nucleotides, and contains long 5' and 3' noncoding regions relative to other pancreatic mRNAs. It encodes a secretory preRNase of 152 amino acid residues including a signal peptide of 25 amino acids.

Two similar but nonallelic rat pancreatic trypsinogens. Nucleotide sequences of the cloned cDNAs.

We have cloned and identified mRNA sequences for two rat pancreatic trypsinogens. Nucleotide sequence analysis of the cloned sequences revealed two mRNAs that encode similar, though noallelic, pretrypsinogens. Trypsinogen I mRNA is 804 nucleotides in length, plus an estimated poly(A) tract of 100 nucleotides, and contains a short (13 nucleotide) 5' noncoding region and a 3' noncoding region of 54 nucleotides. It encodes a preproenzyme of 246 amino acids comprising a hydrophobic prepeptide (signal peptide) of 15 amino acids, an activation peptide characteristic of trypsinogens, and an active form of trypsin, 223 amino acids in length, that has 78% amino acid sequence identity with porcine trypsin. Trypsinogen II mRNA has a nucleotide sequence 88% homologous with that of trypsinogen I mRNA and encodes a protein with 89% amino acid sequence identity with trypsinogen I. The enzymes encoded by trypsinogen I and II mRNAs retain the key amino acid residues that determine the characteristic substrate cleavage preference of trypsins and, therefore, represent the rat counterparts of this digestive enzyme. Trypsinogen I mRNA is a major pancreatic mRNA comprising an estimated 2-5% of the total, whereas trypsinogen II mRNA is present at much lower levels.