Promoter Structure and Regulation

Regulation of transcription of eukaryotic class-II genes with developmental, tissue and hormone-sensitive specificities requires as-yet not understood organization and genome-wide co-ordination of signalling by many regulators. The genome-wide co-ordinated assembly of these regulators into higher-order complexes with target genes, to effect precisely timed changes in transcriptional activity, is one of the great remaining 'black boxes' in developmental biology. Recent findings on the very tightly controlled genes have generated the notion of 'composite promoters' that have and are necessarily dependent on both a TATA box and an initiator. Thus far most examples of composite promoters have been from viruses that are dependent on usurpation of host transcriptional machinery at precisely the right moment in its life cycle and in just the right host-cell biological context. However, our studies have identified that a cellular gene, juvenile hormone esterase, behaves as a possessing a composite core promoter.

Transcription from the core promoter of the juvenile hormone esterase gene (-61 to +28) requires the presence of both an AT-rich motif (TATA box) and an initiator motif for any transcription to occur, when assayed by either transcription in vitro with lepidopteran Sf9 nuclear extracts (see panel at right) or by transient-transfection assay in Sf9 cells. Additional gel-shift experiments in which both the TATA box and initiator motifs are transversion mutated indicated that at least one additional binding site is utilized (see lower panel at right). Mutational analysis in the transcription-in vitro and cell-transfection assays demonstrated that a 14-bp region from +13 to +27 relative to the transcription start site is also essential for transcription to occur, which is distinct from the 'downstream promoter element' described from some TATA-less genes. The juvenile hormone esterase gene thus appears to be a model of a cellular composite core promoter with a multipartite, indispensible requirement for not just both the TATA box and initiator, but also for at least a third core element as well.

Jones G, Chu YX, Schelling D, Jones D. 2000. Regulation of the juvenile hormone esterase gene by a composite core promoter. Biochem J. 346, 233-40

Jones G, Manczak M, Schelling D, Turner H, Jones D. 1998. Transcription of the juvenile hormone esterase gene under the control of both an initiator and AT-rich motif. Biochem J. 335, 79-84.

Schelling D, Jones G. 1995. Functional identification of the transcription start site and the core promoter of the juvenile hormone esterase gene in Trichoplusia ni. Biochem Biophys Res Commun. 214, 286-94.

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