Cloning of the late genes in the ergosterol biosynthetic pathway ofSaccharomyces cerevisiae—A review

Abstract

Research on the ergosterol biosynthetic pathway in fungi has focused on the identification of the specific sterol structure required for normal membrane structure and function and for completion of the cell cycle. The pathway and its end product are also the targets for a number of antifungal drugs. Identification of essential steps in ergo-sterol biosynthesis could provide new targets for the development of novel therapeutic agents. Nine of the eleven genes in the portion of the pathway committed exclusively to ergosterol biosynthesis have been cloned, and their essentiality for aerobic growth has been determined. The first three genes, ERG9 (squalene synthase), ERG1 (squalene epoxidase), and ERG7 (lanosterol synthase), have been cloned and found to be essential for aerobic viability since their absence would result in the cell being unable to synthesize a sterol molecule. The remaining eight genes encode enzymes which metabolize the first sterol, lanosterol, to ultimately form ergosterol. The two earliest genes, ERG11 (lanosterol demethylase) and ERG24 (C-14 reductase), have been cloned and found to be essential for aerobic growth but are suppressed by mutations in the C-5 desaturase (ERG3) gene and fen1 and fen2 mutations, respectively. The remaining cloned genes, ERG6 (C-24 methylase), ERG2 (D8AE7 isomerase), ERG3 (C-5 desaturase), and ERG4 (C-24(28) reductase), have been found to be nonessential. The remaining genes not yet cloned are the C-4 demethylase and the C-22 desaturase (ERG5).

Expression deconvolution: A reinterpretation of DNA microarray data reveals dynamic changes in cell populations

“…Deletions of the ergosterol biosynthesis genes ERG2, ERG3, ERG4, and ERG5 show cell cycle defects, as does treatment with the compound itraconazole or overexpression of IDI1. All disrupt biosynthesis of ergosterol (39)(40)(41)(42), an essential component of the plasma membrane, secretory vesicles, and mitochondrial respiration. The deletions presumably affect such cell membrane-related processes, although the defects are distributed across the cell cycle.…”

Multiple functions of ergosterol in the fission yeast Schizosaccharomyces pombe

“…Multiple genetic and biochemical studies have culminated in the virtually complete elucidation of the pathway leading to ergosterol (Lees et al, 1995;Parks et al, 1995). The enzymic reactions have been largely defined by identification of erg mutants defective in ergosterol biosynthesis, and by their complementation based on sterol auxotrophy or altered sterol composition.…”

Obtenção de levedura híbrida fluorescente e resistente a nistatina

“…A nistatina é um antibiótico comumente utilizado na área médica como agente antifúngico no tratamento de micoses externas, subcutâneas ou sistêmicas de animais Os antibióticos macrolídeos poliênicos interagem com o ergosterol presente na membrana plasmática causando danos e, consequentemente, a morte celular (LAMPEN et al, 1962;LEES et al, 1995). São caracterizados pela presença de 20-44 anéis de lactona (ésteres cíclicos) e de 3-8 duplas ligações conjugadas como se apresenta na figura abaixo (BOLARD, 1986;HOPWOOD, 1997).…”

“…O esterol possui como função manter a estrutura da membrana, permeabilidade, fornecer rigidez, estabilidade e resistência a estresse físico. Nas Experimentos demonstraram que leveduras incapazes de completar a síntese de ergosterol eram resistentes à nistatina, pois não tinham ergosterol suficiente para permitir a ação desse antibiótico e, portanto, para ocorrer a morte celular os antibióticos do grupo dos poliênicos, ao qual pertence a nistatina, interagem com o ergosterol presente na membrana plasmática formando canais pelos quais extravasam os componentes do citoplasma (LAMPEN et al, 1962;LEES et al, 1995).…”

“…O conhecimento da via biossintética permite identificar facilmente passos que são essenciais na síntese do ergosterol e, dessa forma, melhorar a ação dos antifúngicos (LEES, 1995;SHOBAYASHI et al, 2005).…”