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expression, Regulation 4.1 Development of gene expression in eukaryotic cells. Although much is known about the differential regulation of cellular
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Free Gene Control Latchman 16 PDF Downloads The regulation of tissue- and temporal-specific eukaryotic gene expression and the Eukaryotic gene expression, Regulation 4.1 Development of gene expression in eukaryotic cells. Although much is known about the differential regulation of cellular gene expression, relatively little is known about the process of gene activation during embryogenesis. In the present work, we show that several genes (HSP70, SDHA, and RPS14) undergo stage-specific activation in the sea urchin, Strongylocentrotus purpuratus. The genes are not activated uniformly during development; they are activated at stages when the embryo contains a small number of cell types and is undergoing differentiation. Moreover, the genes are activated during the first 24 hours of development, suggesting that they are subject to regulation by temporal or spatial factors. The N terminus of the sea urchin HSP70 protein contains a nuclear localization signal (NLS), suggesting that the protein is a possible target for the import of proteins from the nucleus to the cytoplasm. The sea urchin HSP70 gene does not contain introns in its coding region and so the mature mRNA must be transported from the nucleus to the cytoplasm. The large size of the HSP70 transcript and the lack of NLSs or putative NLSs in the coding region suggest that the RNA is not transported from the nucleus to the cytoplasm by a mechanism similar to that of mRNAs that contain introns and NLSs. The three promoters, each containing several binding sites for Sp1, act with differential sensitivity during development. Sp1 binds most efficiently to promoters P1 and P3; these two promoters are induced early in development. The least active promoter, P2, is induced later in development, coinciding with the induction of the HSP70 gene. The three promoters have different sensitivities to heat shock and to osmotic shock. The heat shock promoters are most sensitive to heat shock and the osmotic shock promoters are most sensitive to osmotic shock. The HSP70 gene is activated during the normal course of development, but is not induced by heat shock or osmotic shock, suggesting that the gene is regulated by additional regulatory factors. The induction of HSP70 in response to heat shock does not require the heat shock response element (HSE), but does require the heat shock response element-like sequence (HRE-
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