Two cat expression vectors for cloning and generation of 3'- and 5'-deletion mutants

Historical Events That Spawned the Field of Plasmid Biology

This chapter revisits the historical development and outcome of studies focused on the transmissible, extrachromosomal genetic elements called plasmids. Early work on plasmids involved structural and genetic mapping of these molecules, followed by the development of an understanding of how plasmids replicate and segregate during cell division. The intriguing property of plasmid transmission between bacteria and between bacteria and higher cells has received considerable attention. The utilitarian aspects of plasmids are described, including examples of various plasmid vector systems. This chapter also discusses the functional attributes of plasmids needed for their persistence and survival in nature and in man-made environments. The term plasmid biology was first conceived at the Fallen Leaf Lake Conference on Promiscuous Plasmids, 1990, Lake Tahoe, California. The International Society for Plasmid Biology was established in 2004 (www.ISPB.org).

Epigenetic inhibition of lysyl oxidase transcription after transformation by ras oncogene

Lysyl oxidase is an extracellular enzyme involved in connective tissue maturation that also acts as a phenotypic suppressor of the ras oncogene. To understand how this suppressor is controlled, gene transcription was studied and the promoter was characterized. Nuclear runoff transcription assays indicated that the markedly reduced amounts of lysyl oxidase message detected after ras transformation resulted from inhibition of lysyl oxidase transcription. Interferon-mediated phenotypic reversion of ras transformed cells, in which the ras oncogene continued to be expressed, was accompanied by the restoration of lysyl oxidase transcription. Reporter gene assay of a transfected mouse lysyl oxidase promoter indicated that it was active in the transformed background, despite the silencing of the endogenous lysyl oxidase promoter. The detection of comparable amounts of mRNA for transcription factors IRF-1 and IRF-2 in normal and ras-transformed cell lines suggests that the differential transcription of lysyl oxidase was not due to regulation of IRFs. Lysyl oxidase promoter activity was localized to a 126 bp region that includes two consensus TATA boxes with associated confirmed cap signals. Analysis of a human lysyl oxidase promoter sequence indicated similar promoter elements and extensive sequence identity with the mouse promoter. The binding of transcription factor AP2 to sites predicted in the control region was confirmed by DNase footprinting. Lysyl oxidase transcription was stimulated by dexamethasone treatment of cells, but this effect could not be assigned within the approximately 3 kb region tested in reporter gene constructs. The promoter activity of the lysyl oxidase reporter gene construct was completely abolished by in vitro DNA methylation, suggesting that the transcriptional suppression after transformation by the ras oncogene may involve DNA methylation.

Structural organization and promoter analysis of the bovine cytochrome c oxidase subunit VIIc gene. A functional role for YY1

Cytochrome c oxidase (COX) subunit VIIc is one of the nuclear encoded subunits of the 13-subunit holoenzyme that carries out the terminal step in the electron transport chain. We have isolated the gene for this subunit, previously shown to be ubiquitously expressed from a single copy gene in the genome, and show that 167 base pairs of DNA surrounding the transcriptional start site contain the minimal promoter of this gene. This basal promoter contains two YY1 sites and at least one site for NRF-2, which show binding to their cognate factors. Mutation of both YY1 sites eliminates most of the promoter activity. Mutation at the upstream YY1 site significantly reduces the efficiency of transcript initiation at the major start site and thus plays the dominant role in COX7C regulation. COX7C is, thus, the second nuclear gene of COX that is regulated by YY1, suggesting that it is a third common factor, along with NRF-1 and NRF-2, to be associated with COX gene regulation.

Cytochrome c oxidase subunit VIIa liver isoform. Characterization and identification of promoter elements in the bovine gene

Cytochrome c oxidase subunit VIIa is specified by two nuclear genes, one (COX7AH) producing a heart/muscle-specific isoform and the other (COX7AL) a form expressed in all tissues. We have isolated both genes to examine their transcriptional regulation. Here, we characterize the core promoter of COX7AL and show that a 92-base pair region flanking the 5'-end promotes most of the activity of this gene. The 92-bp basal promoter contains sites for the nuclear respiratory factors NRF-1 and NRF-2, which have been shown to contribute to the transcription of a number of nuclear genes involved in mitochondrial respiratory activity, and also at least four Sp1 motifs. We show that both the NRF-1 and NRF-2 binding sites are functional in COX7AL and present evidence suggesting that interaction between the NRF-1 site and an upstream element contributes to expression.

The JC virus minimal core promoter is glial cell specific in vivo

The glial cell specificity of the human papovavirus JC (JCV), an etiologic agent for progressive multifocal leukoencephalopathy, is thought to be due to the presence of both positive and negative regulatory elements upstream of the TATA region within the JCV promoter. Here we report that the JCV minimal core promoter, containing only the TATA box and an 8-bp poly(T) region immediately upstream, is sufficient to initiate transcription of an attached gene in glial cells and functions as an autonomously active initiator. We further define the sequences required for this core promoter's glial cell specificity by appropriate substitution and point mutation analysis. Ectopic expression of Tst-1, a POU domain transcription factor that has been implicated in the regulation of oligodendrocyte development, leads to higher activation of the JCV minimal core promoter in Tst-1-deficient glial cells than in non-glial HeLa cells. These results suggest a requirement for a glial cell coactivator(s) for the optimum activation of the JCV minimal core promoter by Tst-1. A discrete affinity of Tst-1 for the JCV core promoter (Kd, 1.4 x 10(-8) M) is also shown to be optimal for its promoter strength. Mutations within the core promoter that maintain this affinity for Tst-1 show maintenance of promoter strength, whereas mutants carrying a change that results in an increased affinity for Tst-1 show reduced transcriptional activity. These results suggest that moderate affinity of Tst-1 for the JCV TATA region may allow the interaction of some glial cell-specific coactivator(s) along with the basal transcription machinery to direct glial cell-specific transcription from the JCV core promoter.