Non-Mendelian determinant [ISP+] in yeast is a nuclear-residing prion form of the global transcriptional regulator Sfp1 - PubMed (original) (raw)

Non-Mendelian determinant [ISP+] in yeast is a nuclear-residing prion form of the global transcriptional regulator Sfp1

Tatyana Rogoza et al. Proc Natl Acad Sci U S A. 2010.

Abstract

Four protein-based genetic determinants or prions-[SWI(+)], [MCA], [OCT(+)], and [MOT3(+)]-are recent additions to the list of well-known Saccharomyces cerevisiae prions, [PSI(+)], [URE3], and [PIN(+)]. A rapid expansion of this list may indicate that many yeast proteins can convert into heritable prion forms and underscores a problem of prion input into cellular physiology. Here, we prove that the global transcriptional regulator Sfp1 can become a prion corresponding to the prion-like determinant [ISP(+)] described earlier. We show that SFP1 deletion causes an irreversible [ISP(+)] loss, whereas increased SFP1 expression induces [ISP(+)] appearance. Cells that display the [ISP(+)] phenotype contain the aggregated form of Sfp1. Indeed, these aggregates demonstrate a nuclear location. We also show that the phenotypic manifestation of Sfp1 prionization differs from the manifestation of SFP1 deletion. These properties and others distinguish [ISP(+)] from yeast prions described to date.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Fig. 1.

Deletion of the SFP1 changes phenotype of [ISP+] strains from Sup− to Sup+. (A) Growth of [ISP+] strain 25–25-2V-P3982 and _sfp1_Δ derivative of this strain on supplemented minimal medium (SMM)-Lys and SMM-His media allowed monitoring of lys2-87 and his7-1 nonsense suppression. SMM medium was used as a growth control. (B) Cosegregation of Ura+ and Sup+ phenotypes on tetrads of the diploid obtained by crossing the _sfp1_Δ derivative of 25–25-2V-P3982 and [ISP+] strain 5B-P4513. This diploid is heterozygous for SFP1 deletion and homozygous for lys2-87, and it contains the nonchromosomal determinant [ISP+].

Fig. 2.

Fig. 2.

Expression of the SFP1 from a high-copy plasmid induces the dominant, GuHCl-curable nonsuppressor phenotype. (A) The Sup- phenotype induced by SFP1 overexpression is dominant. Crosses of the [_isp_−] strain 5B-P4513 to three strains retaining the Sup- phenotype after loss of _SFP1_-expressing plasmid are shown in lines 1–3. Control crosses of 5B-P4513[_isp_−] to [ISP+] and [_isp_−] variants of 25-25-2V-P3982 are in line 4 and line 5, correspondingly. The SMM-Lys medium does not also contain methionine and threonine, because met13-A1 and thr4-B15 were used as selective markers in this cross. (B) The Sup- phenotype induced by transient SFP1 overexpression changes for Sup+ after GuHCl treatment. The original [_isp_−] strain is shown in line 1, one of the strains retaining Sup- phenotype after plasmid loss is shown in line 2, and subsequent 5 mM GuHCl treatment is shown in line 3.

Fig. 3.

Fig. 3.

Sfp1-GFP hybrid protein forms aggregates in [_ISP+_] cells but not in [_isp_−] cells. Detection of Sfp1-GFP by Western blot with anti-GFP antibody in the pellet and supernatant fractions of cell lysates of [ISP+] cells expressing _SFP1_-GFP from the native SFP1 promoter (lines 1 and 2), Gal1/10 promoter (lines 5 and 6), and [_isp_−] cells (lines 3 and 4).

Fig. 4.

Fig. 4.

Fluorescent assay of Sfp1-GFP's ability to aggregate. [_isp_−] cells (A) and [_ISP+_] cells (B) producing the Sfp1-GFP from the native SFP1 promoter are shown. [_ISP+_] cells obtained by Sfp1-GFP overproduction in [_isp_−] strain are shown in C; [_ISP+_] cells obtained by Sfp1-GFP overproduction in _sfp1_Δ strain are shown in D.

Fig. 5.

Fig. 5.

Nuclear location of Sfp1-GFP aggregates in [_ISP+_] cells. [_ISP+_] cells overproducing the Sfp1-GFP in _sfp1_Δ strain are shown in A, and [_ISP+_] cells producing the Sfp1-GFP from the native SFP1 promoter are shown in B.

Fig. 6.

Fig. 6.

The influences of Sfp1 prionization and Sfp1 absence on the strain growth are opposite. Growth of [ISP+] strain 25–25-2V-P3982 is shown in A. The [_isp_−] derivative of this strain obtained by GuHCl treatment is shown in B; the _sfp1_Δ derivative of [ISP+] is in C, and _sfp1_Δ derivative of [_isp_−] strain is in D. YPD medium was used.

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