The 14‐3‐3 Proteins Encoded by the BMH1 and BMH2 Genes are Essential in the Yeast Saccharomyces cerevisiae and Can be Replaced by a Plant Homologue

Abstract

The 14‐3‐3 proteins comprise a family of highly conserved acidic proteins. Several activities have been ascribed to these proteins, including activation of tyrosine and tryptophan hydroxylases in the presence of calcium/calmodulin‐dependent protein kinase II, regulation of protein kinase C, phospholipase A2 activity, stimulation of exocytosis and activation of bacterial exoenzyme S (ExoS) during ADP‐ribosy‐lation of host proteins. In addition, a plant 14‐3‐3 protein is present in a G‐box DNA/protein‐binding complex. Previously, we isolated the BMH1 gene from Saccharomyces cerevisiae encoding a putative 14‐3‐3 protein. Using the polymerase chain reaction method, we have isolated a second yeast gene encoding a 14‐3‐3 protein (BMH2). While disruption of either BMH1 or BMH2 alone had little effect, it was impossible to obtain viable cells with both genes disrupted. The cDNA encoding a plant 14‐3‐3 protein under the control of the inducible GAL1 promoter complemented the double disruption. Transfer of the complemented double disruptant to a medium with glucose resulted in the appearance of a high percentage of large budded cells. After prolonged incubation, these cells became enlarged with irregular buds and chains of cells defective in cell‐cell separation became visible. These results suggest an essential role of the 14‐3‐3 proteins, possibly at a later stage of the yeast cell cycle. Copyright © 1995, Wiley Blackwell. All rights reserved