S. cerevisiae grows over a wide pH
range, but the molecular response to a pH shift is poorly
understood. We have used DNA macro-arrays to identify alkaline induced
genes. Our data confirms the alkaline induction of ENA1, a
membrane bound sodium pump, that to our knowledge is the only
identified alkaline response gene. We have identified several new
alkaline inducible genes that may support alkaline adaptation. Rim101p
is a zinc finger transcription factor that has homologs in
A. nidulans, Y. lipolytica, and
C. albicans. Disruption of RIM101 homologs inhibits
alkaline responses in these organisms, and impairs the ability of S.
cerevisiae to grow in alkaline media. Thus, RIM101 is
required to adapt to alkaline conditions. How RIM101 carries
out this function is not clear, so we examined alkaline induced
transcription in a rim101 delta strain with DNA arrays. Our
results show that ENA1 is properly induced by alkali in a
rim101 delta strain, suggesting that ENA1 does not
mediate the RIM101 response. However, induction of some of the
newly defined alkaline responsive genes does depend on RIM101.
Confirmation of these responses by Northern analysis is currently
underway, but we believe that our data show that RIM101 is a
positive regulator of some alkaline induced genes. This analysis will
help define the global response to alkaline conditions, elucidate the
role of RIM101 in that response, and perhaps give an indication
of the signal(s) that alkaline conditions generate.
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