Time to Empower Release of Insects Carrying a Dominant Lethal and Wolbachia Against Zika

RIDL (release of insects with dominant lethality) and Wolbachia are 2 potentially powerful tools in the fight against Zika, but their technological advancement is being hampered by policy barriers. In this study, we discuss what could be done to overcome these regulatory deadlocks.

The ORC/Cdc6/MCM2-7 complex facilitates MCM2-7 dimerization during prereplicative complex formation

The replicative mini-chromosome-maintenance 2–7 (MCM2-7) helicase is loaded in Saccharomyces cerevisiae and other eukaryotes as a head-to-head double-hexamer around origin DNA. At first, ORC/Cdc6 recruits with the help of Cdt1 a single MCM2-7 hexamer to form an ‘initial’ ORC/Cdc6/Cdt1/MCM2-7 complex. Then, on ATP hydrolysis and Cdt1 release, the ‘initial’ complex is transformed into an ORC/Cdc6/MCM2-7 (OCM) complex. However, it remains unclear how the OCM is subsequently converted into a MCM2-7 double-hexamer. Through analysis of MCM2-7 hexamer-interface mutants we discovered a complex competent for MCM2-7 dimerization. We demonstrate that these MCM2-7 mutants arrest during prereplicative complex (pre-RC) assembly after OCM formation, but before MCM2-7 double-hexamer assembly. Remarkably, only the OCM complex, but not the ‘initial’ ORC/Cdc6/Cdt1/MCM2-7 complex, is competent for MCM2-7 dimerization. The MCM2-7 dimer, in contrast to the MCM2-7 double-hexamer, interacts with ORC/Cdc6 and is salt-sensitive, classifying the arrested complex as a helicase-loading intermediate. Accordingly, we found that overexpression of the mutants cause cell-cycle arrest and dominant lethality. Our work identifies the OCM complex as competent for MCM2-7 dimerization, reveals MCM2-7 dimerization as a limiting step during pre-RC formation and defines critical mechanisms that explain how origins are licensed.

Evaluation of mutagenic potential of acetamiprid by dominant lethal test on Culex quinquefasciatus

Acetamiprid, a member of the neonicotinoid insecticide family, is a new class of insecticide which has recently entered the market place. It is very selective and provides outstanding control of sucking pests such as aphids and whiteflies of major crops. In the present investigation, dominant lethal test (DLT) is adopted for the evaluation of the genotoxic effects of acetamiprid using Culex quinquefasciatus as an experimental model. In this experiment, the males hatched from larvae treated with LD40 were cross mated with normal females and the results were based on the number of hatched and unhatched eggs laid by these females. The statistical analysis of the results for LD40 treated groups gave the values of 37.526±3.886 as against 5.23±0.77 from the nontreated groups which indicated significant dominant lethality of p<0.01. These results indicated that exposure of pesticides even at small dose level proved deleterious to the genome of mosquito and its subsequent generation.

Genotoxicity evaluation of pesticide profenofos by applying dominant lethal test on Culex quinquefasciatus

The present paper deals with the genotoxicity evaluation of profenofos by applying dominant lethal test (DLT) on Culex quinquefasciatus taken as an experimental model. For this, the males hatched from the larvae treated with LC20 of pesticide were crossmated with normal females and the results were based on the number of hatched and unhatched eggs laid by these females. Mean percentage frequency of unhatched eggs was as low as 3.97 in the normal stocks as compared to treated stocks in which the frequency of unhatched eggs had increasedto 9.50. The statistical analysis of the data from treated groups gave values of 9.50±1.35 as against 3.97± 0.38 in the control groups. Profenofos induced significant (p<0.05) dominant lethality.

Effect of environmental conditionsions on some biological aspects of Drosophila melanogaster Meigen ( Diptera : Drosophilidae ) collected from Saidiya and Tuwaitha regions in Baghdad

The wild populations of the vinegar fly Drosophila melanogaster Meigen from two regions in Baghdad , Saidiya and Tuwaitha were selected for this study to investigating the frequency of the dominant lethality , this parameter was investigated through fecundity and egg hatchability rate which considered as main indicator for the presence of mutation . The results showed that fecundity rate in Saidiya increased with time , so the lowest rate was 65.5 eggs per female in November and the highest was 87.4 eggs in May , the same results was observed for Tuwaitha except a significantly decrease in fecundity rate that was observed in May which was 42.7 eggs , as well as another significant differences between the two regions was observed in March when the rate was in Saidiya more than Tuwaitha . The hatchability rate increased gradually in Saidiya until March which equal 69.3% , then decreased significantly in May and reached 48.6% , meanwhile , in Tuwaitha the highest hatchability rate was 67.6% in November, then it was decreased until March , while in May it decreased significantly to 24.5% . So , the hatchability rate decreased significantly in Tuwaitha if compared with that of Saidiya in March and May , before that , the opposite was in November and there isn’t any significant differences between the two regions in January .

Roles of the CDK Phosphorylation Sites of Yeast Cdc6 in Chromatin Binding and Rereplication

The Saccharomyces cerevisiae Cdc6 protein is crucial for DNA replication. In the absence of cyclin-dependent kinase (CDK) activity, Cdc6 binds to replication origins, and loads Mcm proteins. In the presence of CDK activity, Cdc6 does not bind to origins, and this helps prevent rereplication. CDK activity affects Cdc6 function by multiple mechanisms: CDK activity affects transcription of CDC6, degradation of Cdc6, nuclear import of Cdc6, and binding of Cdc6 to Clb2. Here we examine some of these mechanisms individually. We find that when Cdc6 is forced into the nucleus during late G1 or S, it will not substantially reload onto chromatin no matter whether its CDK sites are present or not. In contrast, at a G2/M nocodazole arrest, Cdc6 will reload onto chromatin if and only if its CDK sites have been removed. Trace amounts of nonphosphorylatable Cdc6 are dominant lethal in strains bearing nonphosphorylatable Orc2 and Orc6, apparently because of rereplication. This synthetic dominant lethality occurs even in strains with wild-type MCM genes. Nonphosphorylatable Cdc6, or Orc2 and Orc6, sensitize cells to rereplication caused by overexpression of various replication initiation proteins such as Dpb11 and Sld2.

Characterization of an Allele-Nonspecific Intragenic Suppressor in the Yeast Plasma Membrane H+-ATPase Gene (PMA1)

We have analyzed the ability of A165V, V169I/D170N, and P536L mutations to suppress pma1 dominant lethal alleles and found that the P536L mutation is able to suppress the dominant lethality of the pma1-R271T, -D378N, -D378E, and -K474R mutant alleles. Genetic and biochemical analyses of site-directed mutants at Pro-536 suggest that this amino acid may not be essential for function but is important for biogenesis of the ATPase. Proteins encoded by dominant lethal pma1 alleles are retained in the endoplasmic reticulum, thus interfering with transport of wild-type Pma1. Immunofluorescence studies of yeast conditionally expressing revertant alleles show that the mutant enzymes are correctly located at the plasma membrane and do not disturb targeting of the wild-type enzyme. We propose that changes in Pro-536 may influence the folding of the protein encoded by a dominant negative allele so that it is no longer recognized and retained as a misfolded protein by the endoplasmic reticulum.