Mutational analysis of the [Het-s] prion analog of Podospora anserina. A short N-terminal peptide allows prion propagation.
The het-s locus is one of nine known het (heterokaryon incompatibility) loci of the fungus Podospora anserina. This locus exists as two wild-type alleles, het-s and het-S, which encode 289 amino acid proteins differing at 13 amino acid positions. The het-s and het-S alleles are incompatible as their coexpression in the same cytoplasm causes a characteristic cell death reaction. We have proposed that the HET-s protein is a prion analog. Strains of the het-s genotype exist in two phenotypic states, the neutral [Het-s*] and the active [Het-s] phenotype. The [Het-s] phenotype is infectious and is transmitted to [Het-s*] strains through cytoplasmic contact. het-s and het-S were associated in a single haploid nucleus to generate a self-incompatible strain that displays a restricted and abnormal growth. In the present article we report the molecular characterization of a collection of mutants that restore the ability of this self-incompatible strain to grow. We also describe the functional analysis of a series of deletion constructs and site-directed mutants. Together, these analyses define positions critical for reactivity and allele specificity. We show that a 112-amino-acid-long N-terminal peptide of HET-s retains [Het-s] activity. Moreover, expression of a mutant het-s allele truncated at position 26 is sufficient to allow propagation of the [Het-s] prion analog.
Coustou
V
V
Laboratoire de Génétique Moléculaire des Champignons Filamenteux, I.B.G.C., UPR CNRS 9026, Bordeaux, France.
Deleu
C
C
Saupe
S J
SJ
Bégueret
J
J
D019943:Amino Acid Substitution; D001203:Ascomycota / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D016296:Mutagenesis; D011328:Prions / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*
D017931:DNA Primers; D011328:Prions