High impact information on SMK1

• We propose that the SMK1 MAP kinase participates in a developmentally regulated signal transduction pathway that coordinates cytodifferentiation events with the transcriptional program [1].
• Molecular and cytologic markers indicate that meiotic development proceeds normally in homozygous smk1-delta 1 diploids through meiosis II [1].
• Second, CAK1 mRNA accumulates during spore development contemporaneously with SMK1 mRNA [2].
• SMK1 encodes a developmentally regulated MAP kinase in yeast that is required for spore wall morphogenesis [2].
• We find that 1,3-beta-glucan synthase activity is elevated in smk1 mutants, suggesting that SMK1 negatively regulates GSC2 [3].

Biological context of SMK1

• All of the phenotypes observed are similar to those found for the deletion of SPS1 or SMK1, two putative components of a sporulation-specific MAP kinase cascade [4].
• C. glabrata has a putative mating-type (MAT) locus and a pheromone gene (MFALPHA2), as well as orthologs of at least 31 other Saccharomyces cerevisiae genes that have no known roles apart from mating or meiosis, including FUS3, IME1 and SMK1 [5].
• Timing of SMK1 expression is determined by another cis-acting DNA sequence termed MSE (for middle sporulation element) [6].
• The secretion of protoxin with the authentic amino acid sequence from the modified SMK1 was significantly increased, whereas the transcription level of SMK1 was not affected in the presence or absence of CUG codon [7].
• In order to express the authentic SMK1 product in Saccharomyces cerevisiae, which uses the universal genetic code, the three CUG codons corresponding to Ser87, Ser137 and Ser206 in the SMK1 gene were changed to universal Ser codons by site-directed mutagenesis [7].

Associations of SMK1 with chemical compounds

• The nucleotide sequence of the SMK1 gene predicts a 222 amino acid preprotoxin with a typical signal sequence, the hydrophobic alpha, an interstitial gamma polypeptide with a putative glycosylation site, and the hydrophilic beta [8].
• The expression of the modified SMK1 gene with universal Ser codons was lethal in S.cerevisiae, as well as that of the unmodified SMK1 gene with the CUG codons [7].

Regulatory relationships of SMK1

• The data indicate that Cak1p functions upstream of Smk1p by activating a protein kinase other than Cdc28p [9].
• The CDK-activating kinase CAK1 can dosage suppress sporulation defects of smk1 MAP kinase mutants and is required for spore wall morphogenesis in Saccharomyces cerevisiae [2].
• The Smk1p MAP kinase negatively regulates Gsc2p, a 1,3-beta-glucan synthase, during spore wall morphogenesis in Saccharomyces cerevisiae [3].
• SMK1 encodes a mitogen-activated protein kinase required for spore morphogenesis that is expressed as a middle sporulation-specific gene [6].
• The SMK1 promoter contains an upstream activating sequence (UASS) that specifically interacts with the transcriptional activator Abf1p [6].

Other interactions of SMK1

• A weakened allele of CDC28 suppresses the sporulation defect of an ama1 null strain and increases the activation state of Smk1 [10].
• Using mass spectrometry, we identify Gsc2p as a Smk1p-associated protein [3].
• Here we show that Ama1, a meiosis-specific activator of the anaphase-promoting complex/cyclosome (APC/C), promotes Smk1 activation during meiosis [10].
• Our data suggest that Smk1 and Rsc1/2 define parallel pathways that converge to provide signaling information and the expression of gene products, respectively, that are required for spore morphogenesis [11].
• Moreover, diploids lacking Rsc1 or Rsc2 show a subset of smk1-like phenotypes [11].

Analytical, diagnostic and therapeutic context of SMK1

• Effects of deletion and site-directed mutagenesis of SMK1 on the lethality and the secretion of the gene products were examined [12].
• However, light and electron microscopy show that smk1 asci are defective in organizing spore wall assembly [1].

References