Variacin, a new lanthionine-containing bacteriocin produced by Micrococcus varians: comparison to lacticin 481 of Lactococcus lactis.

A new lanthionine-containing bacteriocin, variacin, displaying a broad host range of inhibition against gram-positive food spoilage bacteria, has been identified from two strains of Micrococcus varians isolated from meat fermentations. The new bacteriocin was purified, and its amino-terminal end and total amino acid composition were determined. The structural gene was isolated and analyzed. Variacin is resistant to heat and pH conditions from 2 to 10. Its primary sequence shows significant homology to lacticin 481 to Lactococcus lactis, which is more pronounced for the probacteriocin than for the leader sequence. Variacin, like lacticin 481, contains lanthionine and beta-methyllanthionine residues, but its leader sequence clearly resembles nonlantibiotic leader sequences. In particular, the prepeptide contains glycine residues at positions -1 and -2 of the processing site.

Different tissue-specific expression of the amylase gene Amy-1 in mice and rats.

We cloned the rat alpha-amylase gene Amy-1 and compared its structure and expression with its mouse counterpart. The results showed that the general organization of the transcriptionally active rat Amy-1 gene was similar to that of its mouse counterpart; i.e., the rat gene also contained two independent transcriptional promoters. The distance between the two promoters in the rat gene was, however, more than double (6 kilobases) that measured in the mouse gene (2.8 kilobases). In addition, the rat genome also contained an independent, orphonlike version of the weaker Amy-1 promoter, which was transcriptionally silent. In spite of the similar overall organization of the Amy-1 genes in mouse and rat cells, an interesting difference was observed in the expression of the weak promoter in these two closely related rodents. In rats this promoter was significantly active only in liver cells, while in mice it was utilized with similar efficiencies in parotid, liver, and pancrease cells. Moreover, the transcripts produced in rat liver had a very heterogeneous population of 5' ends, located between 180 and 220 nucleotides upstream of the two homologous start sites observed for this promoter in mouse liver, even though the sequences around this region were strongly conserved between the two species.

Nonproductive kappa immunoglobulin genes: recombinational abnormalities and other lesions affecting transcription, RNA processing, turnover, and translation.

Six nonproductive kappa immunoglobulin genes (kappa- alleles) were cloned and sequenced. The structural abnormalities discerned from sequence analysis were correlated with functional lesions at the level of transcription, RNA processing, turnover, and translation. Four kappa- alleles, three containing V kappa genes and one not, are transcribed at normal or even greater than normal rates, the defects in these genes being expressed at various posttranscriptional levels. The other two kappa- alleles, both of which lacked V genes, exhibited greatly depressed yet clearly detectable transcriptional activity. These results are consistent with a hierarchical relationship between enhancer and promoter elements in which the enhancer establishes transcriptional competence at the kappa locus and the promoter (or pseudopromoter) determines the relative level of transcriptional activity. One of the structural abnormalities discovered in this study, a large deletion which removes the entire J kappa region, also provides new insight into the mechanism of VJ and VDJ recombination.

Mouse alpha-amylase loci, Amy-1a and Amy-2a, are closely linked.

We have cloned a contiguous 106 X 10(3) base-pair long stretch of mouse DNA. The isolated chromosomal DNA segment contains the single copy gene Amy-1a that is strongly expressed in the parotid gland and, 23 X 10(3) base-pairs downstream from it, one member of the pancreas-specific Amy-2a oligogene family. At least two of the four Amy-2a genes, including the copy linked to Amy-1a, are efficiently transcribed. The cloned DNA sequences do not appear to specify messenger RNAs other than those encoding alpha-amylase in pancreas, parotid gland or liver. Transcription termination on Amy-1a occurs within 3 X 10(3) base-pairs downstream from the polyadenylation site in both parotid gland and liver, in which this gene is transcribed at different rates from different promoters.

Two promoters of different strengths control the transcription of the mouse alpha-amylase gene Amy-1a in the parotid gland and the liver.

We show that two promoters of different strengths are involved in the tissue-specific expression of the alpha-amylase gene Amy-1a in the parotid gland and the liver of mouse. The weaker of the two promoters directs the synthesis of mRNA with a liver-type leader sequence. This promoter is active in both tissues. A promoter that is about 30-fold stronger is exclusively active in the parotid, where it directs the synthesis of an mRNA with a parotid-specific leader sequence. Neither the parotid nor the liver promoter is used in tissues that do not contain cytoplasmic alpha-amylase mRNAs, such as brain, kidney, and spleen. Nuclear transcripts that are initiated several kilobases upstream of the parotid cap site are detected in several tissues. They are most abundant in brain, and are apparently not processed into alpha-amylase mRNA.