A mitotically inheritable unit containing a MAP kinase module - PubMed (original) (raw)

Comparative Study

. 2006 Sep 5;103(36):13445-50.

doi: 10.1073/pnas.0603693103. Epub 2006 Aug 24.

Affiliations

Comparative Study

A mitotically inheritable unit containing a MAP kinase module

Sébastien Kicka et al. Proc Natl Acad Sci U S A. 2006.

Abstract

Prions are novel kinds of hereditary units, relying solely on proteins, that are infectious and inherited in a non-Mendelian fashion. To date, they are either based on autocatalytic modification of a 3D conformation or on autocatalytic cleavage. Here, we provide further evidence that in the filamentous fungus Podospora anserina, a MAP kinase cascade is probably able to self-activate and generate C, a hereditary unit that bears many similarities to prions and triggers cell degeneration. We show that in addition to the MAPKKK gene, both the MAPKK and MAPK genes are necessary for the propagation of C, and that overexpression of MAPK as that of MAPKKK facilitates the appearance of C. We also show that a correlation exists between the presence of C and localization of the MAPK inside nuclei. These data emphasize the resemblance between prions and a self-positively regulated cascade in terms of their transmission. This thus further expands the concept of protein-base inheritance to regulatory networks that have the ability to self-activate.

PubMed Disclaimer

Conflict of interest statement

Conflict of interest statement: No conflicts declared.

Figures

Fig. 1.

Fig. 1.

PaMKK1 and PaASK1 act upstream of PaMpk1. Protein extracts (20 μg) from a wild-type strain grown for different durations (24, 36, and 48 h) on M2 medium and from the Δ_PaMpk1_, IDC404, and IDC118 mutants grown for 48 h were separated on gels and probed with antibodies that specifically detect the unphosphorylated form (anti-MAPK) and the phosphorylated form (anti-phospho-MAPK) of PaMpk1.

Fig. 2.

Fig. 2.

Overexpression of PaMpk1 enhances CG. (A) Quantification of the overexpression of PaMpk1-HA in the strains indicated. (Upper) Western blotting with anti-HA antibodies. (Lower) Coomassie staining of a gel with the same samples. The fold overexpression compared with wild-type (WT) has been evaluated on four different blots, of which the one presented in the figure is revealed by nitroblue tetrazolium/5-bromo-4-chloro-3-indolyl phosphate. In the three others, the HA-tag was detected with ECL. The values obtained after normalization with the wild-type strain were 1.7 ± 0.3 for surPaMpk1-HA5, 1.5 ± 0.1 for surPaMpk1HA7, 1.7 ± 0.5 for surPaMpk1-HA5 surPaMpk1HA7, 1.4 ± 0.5 for surPaMpk1-HA1, and 3.75 ± 1.0 for surPaMpk1-HA1 surPaMpk1-HA5. CG, ability of the strain to trigger CG. (B) Experimental setup to detect CG and resulting plates. CG is visible in the surPaMpk1-HA1 + surPaMpk1-HA5 overexpressing strain yielding darkly pigmented thalli and is less pronounced in the surPaMpk1-HA1 strain and in the surPaMpk1-HA5 + surPaMpk1-HA7 strain (not shown).

Fig. 3.

Fig. 3.

Localization of PaMpk1-GFP. (A and B) Diffuse localization of PaMpk1-GFP in growing hyphae of a wild-type strain carrying the MGFP4 transgene. (C and D) Typical PaMpk1-GFP nuclear localization in 3-day-old hyphae of a wild-type strain with the MGFP4 transgene. (E and F) Lack of PaMpk1-GFP nuclear localization in 3-day-old hyphae in strains carrying the IDC404 mutation and the MGFP4 transgene. The same result is seen in strains with the IDC118 mutation carrying the MGFP4 transgene. (G and H) Nuclear localization of PaMpk1-GFP in growing hyphae of a _CG AS6_-5 culture carrying the MGFP4 transgene. (I and J) Diffuse localization of PaMpk1-GFP in growing hyphae of an _NG AS6_-5 culture carrying the MGFP4 transgene. A, C, E, G, and I: GFP staining to show PaMpk1-GFP. B, D, F, H, and J: DAPI staining to show nuclei. Arrows point toward nuclei containing PaMpk1.

Fig. 4.

Fig. 4.

Effect of the PaNox1 mutation on PaMpk1. (A) Protein extract of the IDC343 mutant analyzed as in Fig. 1 shows that PaMpk1 is phosphorylated in a strain lacking PaNox1. (B) Lack of nuclear localization of PaMpk1 in 3-day-old hyphae.

Similar articles

Cited by

References

    1. Wickner R. B., Edskes H. K., Roberts B. T., Baxa U., Pierce M. M., Ross E. D., Brachmann A. Genes Dev. 2004;18:470–485. - PubMed
    1. Roberts B. T., Wickner R. B. Genes Dev. 2003;17:2083–2087. - PMC - PubMed
    1. Silar P., Haedens V., Rossignol M., Lalucque H. Genetics. 1999;151:87–95. - PMC - PubMed
    1. Haedens V., Malagnac F., Silar P. Fungal Genet. Biol. 2005;42:564–577. - PubMed
    1. Kicka S., Silar P. Genetics. 2004;166:1241–1252. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources