The yeast repeated element sigma contains a hormone-inducible promoter.

AUTOR(ES)
RESUMO

A genomic clone (lambda ScG7) from Saccharomyces cerevisiae encoded a 650-nucleotide poly(A)-containing [poly(A)+] RNA that was about 50 times more abundant in MATa cells that had been exposed to the peptide pheromone alpha-factor than in untreated cells. This RNA was transcribed from a cluster of repetitive sequences: both intact and truncated delta and sigma elements adjacent to a tRNATrp gene. Strand-specific probes indicated that this RNA initiated within an intact sigma element and contained sigma sequences at its 5' end. MATa cells produced two other prominent poly(A)+ RNAs (500 and 5,300 bases) in response to alpha-factor that were homologous to the same strand of sigma but transcribed from other locations in the genome. Induction of the sigma-related transcripts was rapid, was not blocked by inhibition of protein synthesis, required a functional receptor (STE2 gene product), and hence appeared to be a primary response to pheromone. Pulse-labeling confirmed that accumulation of sigma RNA following alpha-factor administration was accounted for by an increase in its rate of transcription. The sigma RNAs also were induced in MAT alpha cells that had been treated with a-factor, but were not present at significant levels in MATa/MAT alpha diploids. In MATa cells transformed with a plasmid in which the lambda ScG7 sigma element was inserted just upstream of a gene coding for the intracellular form of invertase (SUC2) lacking its own promoter, a new poly(A)+ RNA (2.2 kilobases) appeared in response to alpha-factor that hybridized to both sigma and SUC2 probes, and intracellular invertase activity was elevated about 10-fold within 30 min. Primer extension showed that transcription from the hybrid gene initiated exclusively within the sigma sequence (117 nucleotides from the 3' end of the element).

ACESSO AO ARTIGO

Documentos Relacionados