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Strange Met- yeast.

Tue Feb 22 12:31:49 EST 1994

>   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?

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