Hermes Transposon Mutagenesis Shows [URE3] Prion Pathology Prevented by a Ubiquitin-Targeting Protein: Evidence for Carbon/Nitrogen Assimilation Cross Talk and a Second Function for Ure2p in Saccharomyces cerevisiae

Genetics: A Periodical Record of Investigations Bearing on Heredity and Variation

Herman K. Edskes^1¹ 

[1] Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830^1

关键词: F-box protein;    Gln1p;    Hap4p;    LUG1/YLR352W;    nitrogen catabolite repression;    prion;    Ure2p;    [URE3];   

DOI  :  10.1534/genetics.118.300981

学科分类：医学（综合）

来源: Genetics Society of America

【 摘 要 】

[URE3] is an amyloid-based prion of Ure2p , a regulator of nitrogen catabolism. While most “variants” of the [URE3] prion are toxic, mild variants that only slightly slow growth are more widely studied. The existence of several antiprion systems suggests that some components may be protecting cells from potential detrimental effects of mild [URE3] variants. Our extensive Hermes transposon mutagenesis showed that disruption of YLR352W dramatically slows the growth of [URE3-1] strains. Ylr352wp is an F-box protein, directing selection of substrates for ubiquitination by a “cullin”-containing E₃ ligase. For efficient ubiquitylation, cullin-dependent E₃ ubiquitin ligases must be NEDDylated, modified by a ubiquitin-related peptide called NEDD8 ( Rub1p in yeast). Indeed, we find that disruption of NEDDylation-related genes RUB1 , ULA1 , UBA3 , and UBC12 is also counterselected in our screen. We find that like ylr352w Δ [URE3] strains, ylr352w Δ ure2 Δ strains do not grow on nonfermentable carbon sources. Overexpression of Hap4p , a transcription factor stimulating expression of mitochondrial proteins, or mutation of GLN1 , encoding glutamine synthetase, allows growth of ylr352w ∆ [URE3] strains on glycerol media. Supplying proline as a nitrogen source shuts off the nitrogen catabolite repression (NCR) function of Ure2p , but does not slow growth of ylr352w Δ strains, suggesting a distinct function of Ure2p in carbon catabolism. Also, gln1 mutations impair NCR, but actually relieve the growth defect of ylr352w Δ [URE3] and ylr352w Δ ure2 Δ strains, again showing that loss of NCR is not producing the growth defect and suggesting that Ure2p has another function. YLR352W largely protects cells from the deleterious effects of otherwise mild [URE3] variants or of a ure2 mutation (the latter a rarer event), and we name it LUG1 (lets [URE3]/ ure2 grow).

【 授权许可】

CC BY