Deprotection of centromeric cohesin at meiosis II requires APC/C activity but not kinetochore tension

Genome haploidization involves sequential loss of cohesin from chromosome arms and centromeres during two meiotic divisions. At centromeres, cohesin's Rec8 subunit is protected from separase cleavage at meiosis I and then deprotected to allow its cleavage at meiosis II. Protection of centromeric cohesin by shugoshin-PP2A seems evolutionarily conserved. However, deprotection has been proposed to rely on spindle forces separating the Rec8 protector from cohesin at metaphase II in mammalian oocytes and on APC/C-dependent destruction of the protector at anaphase II in yeast. Here, we have activated APC/C in the absence of sister kinetochore biorientation at meiosis II in yeast and mouse oocytes, and find that bipolar spindle forces are dispensable for sister centromere separation in both systems. Furthermore, we show that at least in yeast, protection of Rec8 by shugoshin and inhibition of separase by securin are both required for the stability of centromeric cohesin at metaphase II. Our data imply that related mechanisms preserve the integrity of dyad chromosomes during the short metaphase II of yeast and the prolonged metaphase II arrest of mammalian oocytes

Effect of Gene SFU1 on Riboflavin Synthesis in Flavinogenic Yeast Candida famata

Riboflavin or vitamin B-2 is a necessary component for all living organisms since it is the precursor of flavin coenzymes FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide), which are involved in numerous enzymatic reactions. Flavinogenic yeastCandida famataoverproduces riboflavin under iron starvation; however, regulation of this process is poorly understood. Regulatory gene SEF1 encoding the transcription activator has been identified. Its deletion blocks yeast's ability to overproduce riboflavin under iron starvation. It is known that, in the pathogenic flavinogenic yeastC. albicans, Sfu1 (GATA-type transcription factor) represses SEF1. It is demonstrated in this study that deletion of the SEF1 gene in wild typeC. famataleads to overproduction of riboflavin

Co-Overexpression of RIB1 and RIB6 Increases Riboflavin Production in the Yeast Candida famata

Riboflavin or vitamin B2 is a water-soluble vitamin and a precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which play a key role as enzyme cofactors in energy metabolism. Candida famata yeast is a promising producer of riboflavin, as it belongs to the group of so-called flavinogenic yeasts, capable of riboflavin oversynthesis under conditions of iron starvation. The role of the particular structural genes in the limitation of riboflavin oversynthesis is not known. To study the impact of overexpression of the structural genes of riboflavin synthesis on riboflavin production, a set of plasmids containing genes RIB1, RIB6, and RIB7 in different combinations was constructed. The transformants of the wild-type strain of C. famata, as well as riboflavin overproducer, were obtained, and the synthesis of riboflavin was studied. It was found that overexpression of RIB1 and RIB6 genes coding for enzymes GTP cyclohydrolase II and 3,4-dihydroxy-2-butanone-4-phosphate synthase, which catalase the initial steps of riboflavin synthesis, elevated riboflavin production by 13-28% relative to the parental riboflavin-overproducing strains

SEF1 and VMA1 Genes Regulate Riboflavin Biosynthesis in the Flavinogenic Yeast Candida Famata

Riboflavin (vitamin B-2) is an important component of the diet of living organisms since it is a precursor of flavin coenzymes FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide) involved in numerous enzymatic reactions. It is known that flavinogenic yeastC. famatais able to perform riboflavin overproduction under conditions of iron deficiency, but the regulation of this process remains unknown. It was shown that the deletion of the SEF1 gene (encoding transcription activator) blocked the ability for riboflavin overproduction under conditions of iron deficiency. It was determined that SEF1 promoters of other flavinogenic yeasts (Candida albicansandCandida tropicalis) fused with SEF1 ORF ofC. famatacan restore the overproduction of riboflavin in the sef1 Delta mutant. The disruption of the VMA1 gene (encoding the vacuolar ATPase subunit A) led to overproduction of riboflavin in C. famatain iron complete medium

Role of the regulatory genes SEF1, VMA1 and SFU1 in riboflavin synthesis in the flavinogenic yeast Candida famata (Candida flareri)

Riboflavin or vitamin B(2)is an essential dietary component for humans and animals that is the precursor of flavin coenzymes flavin mononucleotide and flavin adenine dinucleotide involved in numerous enzymatic reactions. The flavinogenic yeastCandida famataoverproduces riboflavin under iron starvation; however, regulation of this process is poorly understood. Regulatory geneSEF1encoding transcription activator has been identified. Its deletion blocks yeast ability to overproduce riboflavin under iron starvation. It was shown here that theSEF1promoters from other flavinogenic (Candida albicans) and non-flavinogenic (Candida tropicalis) yeasts fused with the open reading frame (ORF) ofSEF1gene fromC. famataare able to restore riboflavin oversynthesis insef1 Delta mutants. It is known that in the pathogenic flavinogenic yeastC. albicans, Sfu1 (GATA-type transcription factor) repressesSEF1.Here, we found that deletion ofSFU1gene in wild-typeC. famataleads to riboflavin oversynthesis. Moreover, it was shown that disruption ofVMA1gene (coding for vacuolar ATPase subunit A) also results in riboflavin oversynthesis inC. famata