Transcription and expression of zein sequences in yeast under natural plant or yeast promoters.
Maize genomic fragments containing the regulatory and coding regions of a zein gene for a low size class 23-kd protein have been inserted in an interspecific Escherichia coli-Saccharomyces cerevisiae expression vector in different constructions. The presence of the inducible GAL1-10 upstream activation site (UAS) allows us to regulate differentially by carbon sources the transcription of the zein gene both under the plant promoter and under the yeast CYC-1 promoter. We found that the zein promoter region is properly recognized at the correct transcription start, while different termination points occur during transcription. The yeast UAS was also shown to function as a typical eukaryotic enhancer regardless of its distance or orientation with respect to the plant promoter. Yeast cells transformed by a plasmid containing a zein sequence fused to a short piece of the CYC-1 gene produced a fused polypeptide, of expected mol. wt, in variable amount from 0.2 to 5% depending on the growth phase conditions.
Coraggio
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Istituto Biosintesi Vegetali, C.N.R., Via Bassini, 15, 20133 Milano, Italy.
Compagno
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C
Martegani
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Ranzi
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BM
Sala
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E
Alberghina
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L
Viotti
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A