Multiple copies of a G-rich element upstream of a cAMP-inducible Dictyostelium gene are necessary but not sufficient for efficient gene expression.

The cysteine proteinase 1 (CP1) and cysteine proteinase 2 (CP2) genes of Dictyostelium discoideum encode co-ordinately expressed mRNA sequences which are inducible by extracellular cAMP. There are short, G-rich sequence elements upstream of both genes and we have previously shown that deletion of these elements from the CP2 gene abolishes cAMP-inducibility. We show here that the G-rich element from the CP1 gene is functionally homologous to that in the CP2 gene by reconstituting cAMP-inducibility in a deletion mutant of the CP2 gene using CP1-derived sequences. Both the CP1 and CP2 genes contain multiple G-rich elements. We show that efficient induction requires at least two copies of the CP1 element and that their relative orientation is unimportant. Two copies of an inverted relative orientation are, however, inactive when moved upstream of their normal position and are incapable of conferring cAMP-inducibility on a heterologous gene. These observations suggest that these sequences are either essential promoter elements, not themselves interacting with the inducer, or that their interaction with a separate class of control sequences is necessary for inducible expression.     

Identification and sequence analysis of the 5' end of the major chicken vitellogenin gene.

We have precisely determined the positions of the first three exons for the major chicken vitellogenin gene (VTG II) by a combination of S1 nuclease protection, primer extension and DNA sequencing experiments. In addition, we have determined the nucleotide sequences of the 5' flanking nuclease hypersensitive sites that we have previously shown are induced during the estrogen mediated activation of the VTG II gene in liver (1). One of these sites is found to be nearly identical to the enhancer core sequence of SV40. A computer assisted analysis of the DNA sequences upstream from the VTG II gene has revealed four short (7 to 9 base pair) sequence elements that are present in similar positions flanking the other major estrogen inducible gene for liver, very low density apolipoprotein II (apoVLDL II). For VTG II, these sequences are located between two of the induced nuclease hypersensitive sites that are liver specific. Sequences homologous to one element, located approximately 100 base pairs upstream from the mRNA cap sites of the VTG II and apoVLDL II genes, are also observed for three estrogen inducible genes that are expressed in the oviduct, although for each of these genes the sequence falls further upstream, between -220 and -200. We suggest that these conserved sequences may be important in mediating the tissue specific responses of these genes to estrogen.     

Level of expression of the tomato rbcS-3A gene is modulated by a far upstream promoter element in a developmentally regulated manner.

By Agrobacterium-mediated transformation we have demonstrated that a 1.10-kilobase promoter sequence from the tomato rbcS-3A gene confers light-inducible and organ-specific expression upon fusion to the bacterial chloramphenicol acetyltransferase gene. A biphasic expression profile was obtained by 5' deletion analysis of this promoter, indicating the presence of both positive and negative regulatory elements. A severe reduction in the level of expression was observed when the 5'-terminal 90 base pairs were deleted from the 1.10-kilobase promoter. DNA sequence elements responsible for light inducibility and organ specificity of the gene reside within the -374 base pairs of the proximal part of the promoter and the sequences spanning from -374 to -205 are essential for promoter function. The DNA sequences upstream from -374 modulate the level of expression in leaf tissue; this modulation is under developmental control.     

A highly conserved repeated DNA element located in the chromosome of Streptococcus pneumoniae.

We report the discovery of a group of highly conserved DNA sequences located, in those cases studied, within intergenic regions of the chromosome of the Gram positive Streptococcus pneumoniae. The S. pneumoniae genome contains about 25 of these elements called BOX. From 5' to 3', BOX elements are composed of three subunits (boxA, boxB, and boxC) which are 59, 45 and 50 nucleotides long, respectively. BOX elements containing one, two and four copies of boxB have been observed; boxB alone was also detected in one instance. These elements are unrelated to the two most thoroughly documented families of repetitive DNA sequences present in the genomes of enterobacteria. BOX sequences have the potential to form stable stem-loop structures and one of these, at least, is transcribed. Most of these elements are located in the immediate vicinity of genes whose product has been implicated at some stage in the process of genetic transformation or in virulence of S. pneumoniae. This location raises the intriguing possibility that BOX sequences are regulatory elements shared by several coordinately controlled genes, including competence-specific and virulence-related genes.