ATPase-dependent auto-phosphorylation of the open condensin hinge diminishes DNA binding.

Condensin, which contains two structural maintenance of chromosome (SMC) subunits and three regulatory non-SMC subunits, is essential for many chromosomal functions, including mitotic chromosome condensation and segregation. The ATPase domain of the SMC subunit comprises two termini connected by a long helical domain that is interrupted by a central hinge. The role of the ATPase domain has remained elusive. Here we report that the condensin SMC subunit of the fission yeast Schizosaccharomyces pombe is phosphorylated in a manner that requires the presence of the intact SMC ATPase Walker motif. Principal phosphorylation sites reside in the conserved, glycine-rich stretch at the hinge interface surrounded by the highly basic DNA-binding patch. Phosphorylation reduces affinity for DNA. Consistently, phosphomimetic mutants produce severe mitotic phenotypes. Structural evidence suggests that prior opening (though slight) of the hinge is necessary for phosphorylation, which is implicated in condensin's dissociation from and its progression along DNA.

Opposing role of condensin hinge against replication protein A in mitosis and interphase through promoting DNA annealing.

Condensin is required for chromosome dynamics and diverse DNA metabolism. How condensin works, however, is not well understood. Condensin contains two structural maintenance of chromosomes (SMC) subunits with the terminal globular domains connected to coiled-coil that is interrupted by the central hinge. Heterotrimeric non-SMC subunits regulate SMC. We identified a novel fission yeast SMC hinge mutant, cut14-Y1, which displayed defects in DNA damage repair and chromosome segregation. It contains an amino acid substitution at a conserved hinge residue of Cut14/SMC2, resulting in diminished DNA binding and annealing. A replication protein A mutant, ssb1-418, greatly alleviated the repair and mitotic defects of cut14-Y1. Ssb1 protein formed nucleolar foci in cut14-Y1 cells, but the number of foci was diminished in cut14-Y1 ssb1-418 double mutants. Consistent with the above results, Ssb1 protein bound to single-strand DNA was removed by condensin or the SMC dimer through DNA reannealing in vitro. Similarly, RNA hybridized to DNA may be removed by the SMC dimer. Thus, condensin may wind up DNA strands to unload chromosomal components after DNA repair and prior to mitosis. We show that 16 suppressor mutations of cut14-Y1 were all mapped within the hinge domain, which surrounded the original L543 mutation site.

Food consumption and serum nutritional status of people living in the Kathmandu valley in Nepal.

OBJECTIVE: The food consumption and serum nutritional status of people living in the Kathmandu valley, Nepal, were examined to obtain actual data for comparison with our previous findings. METHODS: A dietary survey of 45 males and 60 females was carried out in March 1997 by the 24-hr dietary recall method and nutrient intake was calculated from food tables of India and Japan. Fasting venous blood samples were obtained and serum biochemical parameters were measured using clinical kits. RESULTS: The mean body mass index values was at about the same level in both sexes, although the mean percentage body fat of females was higher than that of males, and vice versa for packed red cell volume. The main foods consumed by both sexes, were rice, potatoes, meats, milk & dairy products and vegetables, with a difference in the amounts consumed. Females did not drink alcoholic beverages. The mean daily intakes of energy, protein, lipids, iron and vitamin B group for the males were higher than those for the females, while those of vitamins A and C for the males were lower than those for the females. The mean values of serum biochemical parameters for both sexes were generally at the normal levels, but those of ALT and TG were at the higher end of the normal range. Differences of correlation between food groups and between serum parameters were observed depending on the sex, however, no clear relationship between food and nutrient intake and serum biochemical parameters were observed. CONCLUSIONS: The present food intake study revealed that the amounts of food consumption for both sexes, especially for the females, were mostly insufficient although the serum parameters were at the normal levels. The energy intake of both sexes was lower than that of estimated requirements and those in Terai region. The relatively high serum TG level of the subjects may be due to the consumption of large amounts of cereals containing much carbohydrate. Our findings suggested a marked influence on food consumption by food price and income in spite of the easier food availability in the city, and also lack of knowledge about nutrients and health, thus there is need for improvement of the nutritional status of this group of people.