Disease relevance of CHS1

• Primers having designs based on highly conserved stretches in the deduced amino acid sequences of chitin synthase (CHS) genes were used in PCR reactions to amplify 600 bp and 366 bp products from the genomic DNA of three major causal agents of chromoblastomycosis [1].
• In Saccharomyces cerevisiae, mutations in FKS1 confer hypersensitivity to the immunosuppressants FK506 and cyclosporin A, while mutations in ETG1 confer resistance to the cell-wall-active echinocandins (inhibitors of 1,3-beta-D-glucan synthase) and, in some cases, concomitant hypersensitivity to the chitin synthase inhibitor nikkomycin Z [2].
• Nikkomycins X and Z, competitive inhibitors of fungal chitin synthase, were evaluated as therapeutic agents in vitro and in mouse models of coccidioidomycosis, histoplasmosis, and blastomycosis [3].

High impact information on CHS1

• When a plasmid encoding a CHS1-lacZ fusion protein is introduced into S. pombe, both enzymatic activities are expressed in the same ratio as in S. cerevisiae, demonstrating that CHS1 encodes the structural gene of chitin synthase [4].
• In all cases, strains with the disrupted gene have a recognizable phenotype, lack measurable chitin synthase activity in vitro but are viable, contain normal levels of chitin in vivo, and mate and sporulate efficiently [4].
• Using degenerate oligonucleotide mixtures designed on the basis of conserved sequences of the Saccharomyces cerevisiae CHS1 and CHS2 polypeptides, a DNA fragment encoding a similar predicted amino acid sequence was amplified from N. crassa genomic DNA [5].
• Chitin synthase 1 plays a major role in cell wall biogenesis in Neurospora crassa [5].
• To investigate the role of chitin synthase in cell wall biogenesis in Neurospora crassa, we cloned a chitin synthase structural gene and examined the consequences of its inactivation [5].

Biological context of CHS1

• Gene disruption experiments led to the conclusion that CHS2 is essential for cell division [Silverman, S.J., Sburlati, A., Slater, M.L. & Cabib, E. (1988) Proc. Natl. Acad. Sci. USA 85, 4735-4739], whereas CHS1 is not [6].
• However, deletion of the CHS1 gene did not affect the phenotype of the gas1 delta mutant and only slightly reduced the chitin content [7].
• CHS1 gene expression did not peak during germ tube formation but remained at low levels in both yeast and hyphal growth [8].
• According to the published sequence of the CHS1 gene, this fragment contains four repeats of a TGAAACA consensus sequence previously identified in the alpha-factor-inducible BAR1 promoter [Kronstad, J. W., Holly, J. A. and MacKay, V. L. (1987) Cell 50, 369-377] [9].
• In order to minimize possible side effects of CHS1-coding sequences on expression and mRNA stability a CHS1::SUC2 chimaeric gene was constructed where 730 bp of the CHS1 promoter region (+20 bp of the coding region) were fused in frame to a fragment of the SUC2 coding region [9].

Anatomical context of CHS1

• Because the presence of Chs1 in the cell abolishes lysis, it is concluded that damage to the cell wall is caused by excessive chitinase activity at acidic pH, which can normally be repaired through chitin synthesis by Chs1 [10].
• Previous cell fractionation studies demonstrated that chitin synthase I activity (CSI) exists in a plasma membrane form and in intracellular membrane-bound particles called chitosomes [11].
• Chs5/6 Complex: A Multiprotein Complex That Interacts with and Conveys Chitin Synthase III from the Trans-Golgi Network to the Cell Surface [12].
• Chitin synthase activity was not detected in intact protoplasts before or after treatment with trypsin [13].
• However, assays showed that membranes of wdchs2Delta mutants were drastically reduced in chitin synthase activity [14].

Associations of CHS1 with chemical compounds

• Mutants defective in chitin synthase III are resistant to Calcofluor and Kluyveromyces lactis killer toxin, they lack alkali-insoluble glucan, and under certain circumstances, they are temperature-sensitive for growth [15].
• The decrease in the amount of chitin in vegetative cells and the absence of chitosan in spores suggested that the mutant dit101 could be defective in a chitin synthase [16].
• Calcofluor staining of the chs-1RIP strain cross-walls, residual chitin synthase activity, and the increased sensitivity of the chs-1RIP strain to Nikkomycin Z suggest that N. crassa produces additional chitin synthase that can participate in cell wall formation [5].
• Together with similar, previously reported experiments on the inactivation of chitin synthase by glutaraldehyde, these results indicate that the enzyme faces the interior of the cell [13].
• Chs2 also shows less sensitivity than Chs1 to inhibition by polyoxin D or sodium chloride, a property that was used to demonstrate the presence of Chs2 in wild-type extracts [17].

Physical interactions of CHS1

• Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase [18].
• Chs5p is a late-Golgi protein required for the polarized transport of the chitin synthase Chs3p to the membrane [19].

Regulatory relationships of CHS1

• These results, together with the previous knowledge that Co2+ stimulates Chs2 and Chs3 but inhibits Chs1 and that the three synthetases differ in their pH optimum, have enabled us to formulate conditions for the specific determination of each synthetase in the presence of the others [20].

Other interactions of CHS1

• We screened Saccharomyces strains for mutants that are synthetically lethal with deletion of the major chitin synthase gene CHS3 [21].
• Chitin synthase III: synthetic lethal mutants and "stress related" chitin synthesis that bypasses the CSD3/CHS6 localization pathway [21].
• KNR4, a suppressor of Saccharomyces cerevisiae cwh mutants, is involved in the transcriptional control of chitin synthase genes [22].
• We identified four Chs4p homologous proteins in Schizosaccharomyces pombe which we named Chr1, Chr2, Chr3 and Chr4 (putative chitin synthase regulatory factor) [23].
• F. oxysporum chs1-, chs2- and chs7-deficient mutants were constructed through targeted gene disruption by homologous recombination [24].

Analytical, diagnostic and therapeutic context of CHS1

• Chitin synthase II is required for normal morphology, septation, and cell separation [15].
• Cloning and sequencing of the PCR products of one of these fungi, Fonsecaea pedrosoi, identified three CHS sequences designated as FpCHS1, FpCHS2 and FpCHS3 [1].
• Microarray analysis confirmed the importance of Mcm1p-mediated DNA bending in maintaining correct gene expression profiles and revealed defects in Mcm1p-mediated repression of Ty elements and in the expression of the cell cycle-regulated YFR and CHS1 genes [25].
• The encoded chitin synthase product (WdChs4p) showed high homology with Chs3p of Saccharomyces cerevisiae and other class IV chitin synthases, and Northern blotting showed that WdCHS4 was expressed at constitutive levels under all conditions tested [26].
• 1. An improved filtration method is introduced to perform kinetic investigations on the chitin synthase reaction [27].

References