Mutational Analysis of the [Het-s] Prion Analog of Podospora anserina: A Short N-Terminal Peptide Allows Prion Propagation

Corresponding author: Sven J. Saupe, Laboratoire de Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaire, Centre National de la Recherche Scientifique, Unité propre de recherche 9026, 1 rue Camille St. Saëns, 33077 Bordeaux Cedex, France., sven.saupe{at}ibgc.u-bordeaux2.fr (E-mail)

Communicating editor: R. H. DAVIS

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.

This article has been cited by other articles:

				R. B. Wickner, H. K. Edskes, B. T. Roberts, U. Baxa, M. M. Pierce, E. D. Ross, and A. Brachmann Prions: proteins as genes and infectious entities Genes & Dev., March 1, 2004; 18(5): 470 - 485. [Full Text] [PDF]

				H. J. P. Dalstra, K. Swart, A. J. M. Debets, S. J. Saupe, and R. F. Hoekstra Sexual transmission of the [Het-s] prion leads to meiotic drive in Podospora anserina PNAS, May 27, 2003; 100(11): 6616 - 6621. [Abstract] [Full Text] [PDF]

				Q. Xiang and N. L. Glass Identification of vib-1, a Locus Involved in Vegetative Incompatibility Mediated by het-c in Neurospora crassa Genetics, September 1, 2002; 162(1): 89 - 101. [Abstract] [Full Text] [PDF]

				S. W. Liebman Progress toward an ultimate proof of the prion hypothesis PNAS, July 9, 2002; 99(14): 9098 - 9100. [Full Text] [PDF]

				S. J. Saupe Molecular Genetics of Heterokaryon Incompatibility in Filamentous Ascomycetes Microbiol. Mol. Biol. Rev., September 1, 2000; 64(3): 489 - 502. [Abstract] [Full Text] [PDF]