A mutant yeast in which a weak GAL4-derived activator functions as a strong activator bears a single mis-sense mutation in GAL11 (a.k.a. SPT13). The first 74 amino acids of GAL4, including the zinc-dependent DNA binding region, attached to an acidic activating sequence, are sufficient to respond both to GAL11 and to our mutant GAL11P (potentiator). PPR1, a yeast activator with a similar zinc finger sequence, also responds to GAL11 and to GAL11P, whereas regulators bearing unrelated DNA binding motifs do not. GAL11 itself works as a strong activator when tethered to DNA by fusion to the bacterial LexA protein, and deletion of GAL11 is known to cause a 5- to 10-fold reduction in GAL4 activity. We suggest that a complex of GAL4 and GAL11 constitutes a particularly strong activator; evidence that the putative GAL4-GAL11 complex ordinarily forms preferentially on DNA suggests a biological rationale for GAL11 action.

• PMID: 2124519
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Comparative Study | Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, P.H.S.

Authors

Himmelfarb HJ, Pearlberg J, Last DH, Ptashne M

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