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Dolichols are isoprenoid lipids of varying length that act as sugar carriers in glycosylation reactions in the endoplasmic reticulum. In Saccharomyces cerevisiae , there are two cis -prenyltransferases that synthesize polyprenol-an essential precursor to dolichol. These enzymes are heterodimers composed of Nus1 and either Rer2 or Srt1. Rer2-Nus1 and Srt1-Nus1 can both generate dolichol in vegetative cells, but srt1 ∆ cells grow normally while rer2 ∆ grows very slowly, indicating that Rer2-Nus1 is the primary enzyme used in mitotically dividing cells. In contrast, SRT1 performs an important function in sporulating cells, where the haploid genomes created by meiosis are packaged into spores. The spore wall is a multilaminar structure and SRT1 is required for the generation of the outer chitosan and dityrosine layers of the spore wall. Srt1 specifically localizes to lipid droplets associated with spore walls, and, during sporulation there is an SRT1 -dependent increase in long-chain polyprenols and dolichols in these lipid droplets. Synthesis of chitin by Chs3, the chitin synthase responsible for chitosan layer formation, is dependent on the cis -prenyltransferase activity of Srt1, indicating that polyprenols are necessary to coordinate assembly of the spore wall layers. This work shows that a developmentally regulated cis -prenyltransferase can produce polyprenols that function in cellular processes besides protein glycosylation., (Copyright © 2017 by the Genetics Society of America.)

Introduction: Prostrate cancer (PC) is one of the most common malignancies and is frequently treated with an 8-week course of radiotherapy. CyberKnife (CK) based radioablation enables completion of therapy within 5-9 days. The aim of this study is an evaluation of the effectiveness and tolerance of CyberKnife-based radioablation in prostate cancer patients., Material and Methods: 200 PC patients (94 low risk [LR], 106 intermediate risk [IR]) underwent CK irradiation every other day (fraction dose [fd] 7.25 Gy, total dose [TD] 36.25 Gy, time 9 days). PSA varied from 1.1 to 19.5 (median 7.7) and T stage from T1c to T2c. The percentage of patients with Androgen Deprivation Therapy (ADT), GI (gastrointestinal) and GU (genitourinary) toxicity (EORTC/RTOG scale), and PSA were checked at 1, 4 and 8 months, and thereafter every 6 months - up to a total of 26 months - post-treatment., Results: The percentage of patients without ADT increased from 47.5% to 94.1% after 26 months. The maximum percentage of acute G3 adverse effects was 0.6% for GI, 1% for GU and G2 - 2.1% for GI and 8.5% for GU. No late G3 toxicity was observed. The maximum percentage of late G2 toxicity was 0.7% for GI and 3.4% for GU. Median PSA decreased from 7.7 to 0.1 ng/ml during FU. One patient relapsed and was treated with salvage brachytherapy., Conclusions: We conclude that CK-based radioablation in low and intermediate risk PC patients is an effective treatment modality enabling OTT reduction and presents a very low percentage of adverse effects.

Peritoneal ultrafiltration and dialysis is a feasible therapy in selected patients with heart failure (HF). This method is effective in slow and continuous plasma volume reduction, maintenance of normonatraemia, the removal of cytokines and humoral factors involved in the development and progression of HF and middle-molecule clearance. We present a 26-year-old woman with HF refractory to conventional treatment. Peritoneal dialysis improved both the clinical status and the quality of life. Peritoneal dialysis is an invasive method of treatment therefore more studies are necessary to identify patients who would benefit from this form of therapy.

In the yeast Saccharomyces cerevisiae the RER2 and SRT1 genes encode Rer2 and Srt1 proteins with cis-prenyltransferase (cis-PT-ase) activity. Both cis-PT-ases utilize farnesyl diphosphate (FPP) as a starter for polyprenyl diphosphate (dolichol backbone) formation. The products of the Rer2 and Srt1 proteins consist of 14-17 and 18-23 isoprene units, respectively. In this work we demonstrate that deletion or overexpression of SRT1 up-regulates the activity of Rer2p and dolichol content. However, upon overexpression of SRT1, preferential synthesis of longer-chain dolichols and a decrease in the amount of the shorter species are observed. Furthermore, overexpression of the ERG20 gene (encoding farnesyl diphosphate synthase, Erg20p) induces transcription of SRT1 mRNA and increases the levels of mRNA for RER2 and DPM1 (dolichyl phosphate mannose synthase, Dpm1p). Subsequently the enzymatic activity of Rer2p and dolichol content are also increased. However, the amount of Dpm1p or its enzymatic activity remain unchanged.

Dimethylallyl diphosphate, an isomer of isopentenyl diphosphate, is a common substrate of Mod5p, a tRNA modifying enzyme, and the farnesyl diphosphate synthase Erg20p, the key enzyme of the isoprenoid pathway. rsp5 mutants, defective in the Rsp5 ubiquitin-protein ligase, were isolated and characterized as altering the mitochondrial/cytosolic distribution of Mod5p. To understand better how competition for the substrate determines the regulation at the molecular level, we analyzed the effect of the rsp5-13 mutation on Erg20p expression. The level of Erg20p was three times lower in rsp5-13 compared to the wild type strain and this effect was dependent on active Mod5p. Northern blot analysis indicated a regulatory role of Rsp5p in ERG20 transcription. ERG20 expression was also impaired in pkc1Delta lacking a component of the cell wall integrity signaling pathway. Low expression of Erg20p in rsp5 cells was accompanied by low level of ergosterol, the main end product of the isoprenoid pathway. Additionally, rsp5 strains were resistant to nystatin, which binds to ergosterol present in the plasma membrane, and sensitive to calcofluor white, a drug destabilizing cell wall integrity by binding to chitin. Furthermore, the cell wall structure appeared abnormal in most rsp5-13 cells investigated by electron microscopy and chitin level in the cell wall was increased two-fold. These results indicate that Rsp5p affects the isoprenoid pathway which has important roles in ergosterol biosynthesis, protein glycosylation and transport and in this way may influence the composition of the plasma membrane and cell wall.

Dolichol, an isoprenoid lipid, known mainly for its function in protein glycosylation, is synthesised in the mevalonate pathway. The pathway is highly regulated, on multiple levels, by sterol and non-sterol derivatives of mevalonic acid. Farnesyl diphosphate (FPP) and/or FPP-derived molecules have been identified as the main non-sterol compounds regulating degradation of 3-hydroxy-3-methylglutaryl-CoA reductase, one of the regulatory enzymes in the mevalonate pathway. In the present review we concentrate on the effect of overexpression of farnesyl diphosphate synthase on dolichol biosynthesis in yeast. In this context the role of the Yta7 protein, belonging to the AAA ATPase family, in the regulation of FPP flux to the dolichol branch of the mevalonate pathway is discussed, and the effect of FPP and/or derived molecules on the transcription of genes encoding the first enzyme committed to dolichol biosynthesis, i.e. cis-prenyl transferase.

tRNA isopentenylation is a branch of an isoprenoid pathway in yeast. There is a competition for a substrate between isoprenoid biosynthetic enzyme Erg20p and tRNA isopentenyltransferase. Here we studied the direct effect of elevated tRNA biosynthesis on ERG20 expression. The maf1-1 mutant of Saccharomyces cerevisiae that has enhanced cellular tRNA levels was used. We show that both ERG20 transcript and Erg20 protein levels are increased in maf1-1. Additionally, maf1-1 leads to decreased ergosterol content in the cells. These effects of maf1-1 are dependent on functional tRNA isopentenyltransferase. Our results indicate that a complex regulation of the isoprenoid pathway involves also an effect of changes in tRNA biosynthesis.