High impact information on SKT5

• This localization depends on the septins but not on Chs4p or Chs3p [1].
• A GFP-Chs4p fusion protein also localizes to a ring at the mother-bud neck on the mother-cell side [1].
• Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4(V831A/F833A) to localize properly [2].
• GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4(V831A/F833A) mutant but does mobilize to the neck at cytokinesis [2].
• In conclusion, S. cerevisiae contains two functionally redundant genes in the control of CSIII activity: CHS4, whose function is restricted to vegetative growth because Chs4p is rapidly degraded during sporulation, and SHC1, whose function in cell wall ascospore assembly is transcriptionally restricted to the sporulation process [3].

Biological context of SKT5

• Disruption of CHS4 in C. albicans yielded a Calcofluor-resistant phenotype, indicating that Chs4p contributes to chitin biosynthesis [4].
• CHS4 encodes a 696 amino acids protein with no potential transmembrane domain. chs4-null mutants are resistant to Calcofluor white and exhibit a considerable reduction in cell wall chitin and in chitin synthase III (CSIII) activity [5].
• Chs4p does not act as a transcriptional or translational regulator of CHS3, the gene coding for the catalytic subunit of CSIII activity, and we therefore propose that Chs4p would be an essential component of the CSIII complex, acting as a post-translational regulator of this activity [5].
• Neither the EF-hand motif nor a possible prenylation site in Chs4p was required for these activities [6].
• The DNA sequence analysis of the cloned mutant skt5 gene showed a nucleotide substitution (causing a glycine-to-glutamic acid substitution) and also a nucleotide insertion (causing a frameshift at the extreme carboxyterminal region) in the structural region from its wild-type gene [7].

Anatomical context of SKT5

• Approximately half of the Chs3p activity in the membranes of cells overexpressing Chs4p was extracted using CHAPS and cholesteryl hemisuccinate [6].
• A mutant allele skt5 affecting protoplast regeneration and killer toxin resistance has double mutations in its wild-type structural gene in Saccharomyces cerevisiae [7].

Regulatory relationships of SKT5

• Consistent with this, overexpression of Chs4p under the regulation of the ScGAL1 promoter enhanced chitin synthase 3 activity in S. cerevisiae 7- to 38-fold [4].

Other interactions of SKT5

• We identified four Chs4p homologous proteins in Schizosaccharomyces pombe which we named Chr1, Chr2, Chr3 and Chr4 (putative chitin synthase regulatory factor) [8].
• EhCHS-1 is deposited chitin in the lateral wall of transformed Saccharomyces cerevisiae Chs mutants, independent of accessory proteins (Chs4p to Chs7p) required by yeast Chs3p [9].

Analytical, diagnostic and therapeutic context of SKT5

• Western blotting confirmed that Chs3p was extracted from membranes by CHAPS and cholesteryl hemisuccinate and revealed that Chs4p was also solubilized using these detergents [6].

References