>> We are working on the S.cerevisiae bHLH-ZIP protein CPF1 (Centromere and
>Promoter Factor). CPF1 binds DNA at both centromeres and in lots of promoters
>including those of various MET genes. When you delete the CPF1 gene you get
>methionine auxotrophy. However, CPF1 does not act as a simple activator at
>these sites. We, in fact, cannot find a site at which CPF1 actually affects
>transcription in any major way. In our attempts to look at this problem we
>have tried various ways of suppressing the Met- phenotype of cpf1- yeast.
>These turn out to include:
>>1. Secondary mutations in SPT21, SIN3, RPD3 and CCR4.
>>2. Over expression of PHO4, and mutations in PHO80 or PHO84.
>>3. When we lower the concentration of all the amino acids in our minus Met
>media (for instance 0.5X standard Guthrie and Fink mix).
>>Okay, are you still with me? :-)
>>The weird one is point 3. When we use a 0.5X amino acid mix but omit either
>aspartate or threonine we get our Met- phenotype back again.
>>So, the question (finally), is: Does anybody know of a link between the MET
>system, the PHO system and the Asp and Thr pathways (other than "they
>are all in yeast and involve metabolism! :-))? Or, does anyone have an
>explanation for point 3?
Does a cpf1- strain have a Thr- or Asp- phenotype?