High impact information on SMI1

• We cloned and sequenced the SMI1 gene, which encodes a 57-kDa polypeptide with evolutionarily conserved epitope(s) found in mammalian cell nuclei [1].
• Another mutant (smi1) exhibited a rare phenotype at the nonpermissive condition, which included S phase and budding arrest [1].
• Disruption of the KNR4 locus does not result in cell death; however, it leads to reduced levels of both (1,3)-beta-glucan synthase activity and (1,3)-beta-glucan content in the cell wall [2].
• In this paper, we demonstrate by two-hybrid, in vitro immunoprecipitation and tandem affinity purification (TAP) methods that Knr4p physically interacts with Slt2p [3].
• KNR4, a suppressor of Saccharomyces cerevisiae cwh mutants, is involved in the transcriptional control of chitin synthase genes [4].

Biological context of SMI1

• The KNR4 gene, originally isolated by complementation of a K9 killer-toxin-resistant mutant displaying reduced levels of both 1,3-beta-glucan and 1,3-beta-glucan synthase activity, was recloned from a YCp50 genomic library as a suppressor of Saccharomyces cerevisiae calcofluor-white-hypersensitive (cwh) mutants [4].
• In addition, it is shown that the efficiency of spores formation was drastically reduced in diploid cells homozygous for the disruption of KNR4 or for a temperature-sensitive mutation of TYS1, although this effect could be independent of their protein interaction [5].
• Moreover, the replacement of the two in vivo phosphorylated Ser(200) and Ser(203) by alanines led to a mutated protein with reduced protein interactions and a weaker complementation ability towards knr4 null mutant phenotypes [6].
• These results together with previous data from genome scale two-hybrid and synthetic interaction screens support the notion that Knr4 is a regulatory protein that participates in the coordination of cell wall synthesis with bud emergence, and that this function may be modulated by phosphorylation of this protein [6].
• Furthermore, the cell wall biogenesis protein KNR4 which physically interacts with TyrRS and cooperates in beta-1,3 glucan biosynthesis falls into a single gene cluster with TyrRS [7].

Anatomical context of SMI1

• The interaction of Slt2 MAP kinase with Knr4 is necessary for signalling through the cell wall integrity pathway in Saccharomyces cerevisiae [3].

Associations of SMI1 with chemical compounds

• In these mutants, which were characterized by increased chitin levels, the suppressor effect of KNR4 resulted, for some of them, in a lowering of polymer content to close to wild-type level, with no effect on the contents of beta-glucan and mannan [4].
• Interaction of Knr4 protein, a protein involved in cell wall synthesis, with tyrosine tRNA synthetase encoded by TYS1 in Saccharomyces cerevisiae [5].
• In exponentially growing cells on glucose, Knr4 appeared to be present in a protein complex that migrates with an apparent Mw superior to 250 kDa [6].

Other interactions of SMI1

• Overexpression of either of the two genes in a wild-type strain led to increased resistance to wall-affecting drugs, while this effect was not obtained in a bck2 Delta mutant that overexpressed KNR4 [8].

References