Truncated forms of a novel XXXX protein suppress the lethality of a G protein alpha subunit deficiency by interacting with the beta subunit.

@entity5680 @entity33691 @entity5679 @entity32350 @entity34215 @entity73201 @entity375 @entity5681
In @entity375 , the mating @entity5681 -initiated signal is transduced by a heterotrimeric G protein and normally results in transient cell cycle arrest and differentiation. A null allele of the G alpha ( @entity33691 / @entity33691 ) subunit results in cell death due to unchecked signaling from the G beta gamma ( @entity5679 , @entity5680 , respectively) heterodimer. We have identified three high copy suppressors of @entity33691 lethality. Two of these genes encode known transcription factors. Mat @entity34215 and @entity32350 . The third is a truncated form of a novel gene, @entity73201 . Overexpressed wild type @entity73201 is a weak suppressor of @entity33691 . In contrast, the isolated mutant allele @entity73201 -1 is a strong suppressor that completely blocks the cell cycle arrest and differentiation phenotypes of @entity33691 cells of both mating types. One deletion mutant ( @entity73201 delta 340) can suppress the cell cycle arrest associated with @entity33691 , but the cells retain a differentiated morphology. @entity73201 -1 can suppress the effects of overexpressed wild type G beta but is not able to suppress the lethality of an activated G beta mutant (STE4Hpl). Consistent with these genetic observations, the suppressing form of @entity73201 can interact with the @entity5679 gene product, as determined by a two-hybrid assay. @entity73201 -1 is also capable of promoting @entity5681 recovery in wild type cells, as judged by halo assay. The sequence of @entity73201 predicts eight membrane-spanning domains. Deletion mutants of @entity73201 indicate that complete @entity33691 suppression requires removal of all of these hydrophobic regions. Interestingly, this truncated protein localizes to the same plasma membrane-enriched subcellular fraction as does full-length @entity73201 . Three hypothetical @entity375 proteins, identified by their similarity to the @entity73201 primary sequence within the @entity33691 suppression domain, also appear to have related structures. The properties of @entity73201 are consistent with those of a transmembrane signaling component that can respond to, or transduce signals through, G beta or G beta gamma.
