Inverted repeat-stimulated sister-chromatid exchange events are RAD1-independent but reduced in a msh2 mutant

Inverted repeats (IRs) and trinucleotide repeats (TNRs) that have the potential to form secondary structures in vivo are known to cause genome rearrangements. Expansions of TNRs in humans are associated with several neurological disorders. Both IRs and TNRs stimulate spontaneous unequal sister-chromatid exchange (SCE) in yeast. Secondary structure-associated SCE events occur via double-strand break repair. Here we show that the rate of spontaneous IR-stimulated unequal SCE events in yeast is significantly reduced in strains with mutations in the mismatch repair genes MSH2 or MSH3, but unaffected by a mutation in the nucleotide excision-repair gene RAD1. Non-IR-associated unequal SCE events are increased in both MMR- and rad1-mutant cells; however, SCE events for both IR- and non-IR-containing substrates occur at a higher level in the exo1 background. Our results suggest that spontaneous SCE occurs by a template switching mechanism. Like IRs, TNRs have been shown to generate double-strand breaks (DSBs) in yeast. TNR expansions in mice are MSH2-dependent. Since IR-mediated SCE events are reduced in msh2 cells, we propose that TNR expansion mutations arise when DSBs are repaired using the sister or the homolog as a template

Long Palindromic Sequences Induce Double-Strand Breaks during Meiosis in Yeast

Inverted-repeated or palindromic sequences have been found to occur in both prokaryotic and eukaryotic genomes. Such repeated sequences are usually short and present at several functionally important regions in the genome. However, long palindromic sequences are rare and are a major source of genomic instability. The palindrome-mediated genomic instability is believed to be due to cruciform or hairpin formation and subsequent cleavage of this structure by structure-specific nucleases. Here we present both genetic and physical evidence that long palindromic sequences (>50 bp) generate double-strand breaks (DSBs) at a high frequency during meiosis in the yeast Saccharomyces cerevisiae. The palindrome-mediated DSB formation depends on the primary sequence of the inverted repeat and the location and length of the repeated units. The DSB formation at the palindrome requires all of the gene products that are known to be responsible for DSB formation at the normal meiosis-specific sites. Since DSBs are initiators of nearly all meiotic recombination events, most of the palindrome-induced breaks appear to be repaired by homologous recombination. Our results suggest that short palindromic sequences are highly stable in vivo. In contrast, long palindromic sequences make the genome unstable by inducing DSBs and such sequences are usually removed from the genome by homologous recombination events

Disruption of Four Kinesin Genes in <it>Dictyostelium</it>

Abstract Background Kinesin and dynein are the two families of microtubule-based motors that drive much of the intracellular movements in eukaryotic cells. Using a gene knockout strategy, we address here the individual function(s) of four of the 13 kinesin proteins in Dictyostelium. The goal of our ongoing project is to establish a minimal motility proteome for this basal eukaryote, enabling us to contrast motor functions here with the often far more elaborate motor families in the metazoans. Results We performed individual disruptions of the kinesin genes, kif4, kif8, kif10, and kif11. None of the motors encoded by these genes are essential for development or viability of Dictyostelium. Removal of Kif4 (kinesin-7; CENP-E family) significantly impairs the rate of cell growth and, when combined with a previously characterized dynein inhibition, results in dramatic defects in mitotic spindle assembly. Kif8 (kinesin-4; chromokinesin family) and Kif10 (kinesin-8; Kip3 family) appear to cooperate with dynein to organize the interphase radial microtubule array. Conclusion The results reported here extend the number of kinesin gene disruptions in Dictyostelium, to now total 10, among the 13 isoforms. None of these motors, individually, are required for short-term viability. In contrast, homologs of at least six of the 10 kinesins are considered essential in humans. Our work underscores the functional redundancy of motor isoforms in basal organisms while highlighting motor specificity in more complex metazoans. Since motor disruption in Dictyostelium can readily be combined with other motility insults and stresses, this organism offers an excellent system to investigate functional interactions among the kinesin motor family.</p

Effects of anticonvulsant drug on liver enzymes among children in a tribal state of India: A longitudinal study

Introduction: Epilepsy is a syndrome of various neurological disorders. Idiosyncratic hepatotoxicity is a rare adverse effect associated with antiepileptic drugs (AED) therapy. Antiepileptic drugs may produce hepatic injury as part of a more widespread hypersensitivity reaction. Laboratory monitoring of asymptomatic effects may allow for the early detection of hepatotoxicity. So the present prospective longitudinal study was carried out to determine the effects of Anticonvulsant drug on liver enzymes among Epileptic Children. Materials Methods: A prospective observational study was conducted among children with seizure disorder attending Paediatric outdoor patient Department of Rajendra Institute of Medical Sciences, Ranchi from February 2014 to October 2015. 50 children with newly diagnosed or untreated seizure disorder were included in case and 50 children of both sexes with same age group as cases were selected as control who did not have seizure. Children with age ranging from 2-10 years were included by consecutive sampling technique. Data was analysed using Statistical Package for Social Sciences (SPSS) software version 25(IBM Corp., Armonk, NY, USA). Paired t test was used to compare the mean values of liver enzymes amongst the children.”P-value” was considered to be non – significant if found ≥ 0.05 and significant if P-value was found to be <0.05. Results: In the present study there was no significant alteration of hepatic profile after treatment with valproate except serum alkaline phosphatase which was increased from the initial value than control group and was statistically significantly with P value of less than 0.05. Conclusion: We concluded that these Antiepileptic drugs are safe to use in children up to 1 year

S-Adenosyl-Homocysteine Is a Weakly Bound Inhibitor for a Flaviviral Methyltransferase

<div><p>The methyltransferase enzyme (MTase), which catalyzes the transfer of a methyl group from S-adenosyl-methionine (AdoMet) to viral RNA, and generates S-adenosyl-homocysteine (AdoHcy) as a by-product, is essential for the life cycle of many significant human pathogen flaviviruses. Here we investigated inhibition of the flavivirus MTase by several AdoHcy-derivatives. Unexpectedly we found that AdoHcy itself barely inhibits the flavivirus MTase activities, even at high concentrations. AdoHcy was also shown to not inhibit virus growth in cell-culture. Binding studies confirmed that AdoHcy has a much lower binding affinity for the MTase than either the AdoMet co-factor, or the natural AdoMet analog inhibitor sinefungin (SIN). While AdoMet is a positively charged molecule, SIN is similar to AdoHcy in being uncharged, and only has an additional amine group that can make extra electrostatic contacts with the MTase. Molecular Mechanics Poisson-Boltzmann Sovation Area analysis on AdoHcy and SIN binding to the MTase suggests that the stronger binding of SIN may not be directly due to interactions of this amine group, but due to distributed differences in SIN binding resulting from its presence. The results suggest that better MTase inhibitors could be designed by using SIN as a scaffold rather than AdoHcy.</p> </div