An innovative method of Diaspis echinocacti Bouche control using DNA insecticide onOpuntia ficus-indica (L.) Mill. in the Nikitsky Botanical Garden, Crimea

Aim. Investigation of the effectiveness of a DNA insecticide with a high level of environmental friendliness on Diaspis echinocacti Bouche in the greenhouse of the Nikitsky Botanical Garden.Materials and Methods. The object of the study was the insect pest Diaspis echinocacti Bouche. The number of D. echinocacti larvae was identified on segments of Opuntia ficus-indica L. (Mill.) using a Nikon SMZ 745T microscope and computer microphotography. In the experiment, the effectiveness of the DNA insecticide "Cactus-NBG" on D. echinocacti was studied, the preparation "Tanrek VK", VRK, from the class of neonicotinoids being used as a standard insecticide.Results. It was revealed that the treatment with the DNA insecticide "Cactus-NBG" against D. echinocacti larvae had a significant insecticidal effect. The biological effectiveness of the preparation was 82.0%. The mortality of larvae after treatment significantly increased in comparison with the control (p<0.05) and was measured at 43.2±5.0%, 53.2±2.3%, and 84.2±2.2% on the 3rd, 7th, and 14th day after treatment respectively.Conclusion. As a result of treatment of O. ficus-indica against D. echinocacti with the contact DNA insecticide "Cactus-NBG", a significant insecticidal effect was found. On the 14th day after treatment, the mortality of D. echinocacti in "Cactus-NBG" was 84.2±2.2%, in the "Tanrek" group - 86.0±1.4% and in the control group treated with water -11.2±1.2%. The biological effectiveness of "Cactus-NBG" on the 14th day was 82.0%. Thus, the preparation "Cactus-NBG", based on the antisense fragment of the D. echinocacti genome, caused a significant mortality of the target insect pest and can compete with modern chemical preparations.

Chromatin remodelling comes into focus

ATP-dependent chromatin remodelling enzymes are molecular machines that act to reconfigure the structure of nucleosomes. Until recently, little was known about the structure of these enzymes. Recent progress has revealed that their interaction with chromatin is dominated by ATPase domains that contact DNA at favoured locations on the nucleosome surface. Contacts with histones are limited but play important roles in modulating activity. The ATPase domains do not act in isolation but are flanked by diverse accessory domains and subunits. New structures indicate how these subunits are arranged in multi-subunit complexes providing a framework from which to understand how a common motor is applied to distinct functions.

CryoEM structures of human CMG–ATPγS–DNA and CMG–AND-1 complexes

DNA unwinding in eukaryotic replication is performed by the Cdc45–MCM–GINS (CMG) helicase. Although the CMG architecture has been elucidated, its mechanism of DNA unwinding and replisome interactions remain poorly understood. Here we report the cryoEM structure at 3.3 Å of human CMG bound to fork DNA and the ATP-analogue ATPγS. Eleven nucleotides of single-stranded (ss) DNA are bound within the C-tier of MCM2–7 AAA+ ATPase domains. All MCM subunits contact DNA, from MCM2 at the 5′-end to MCM5 at the 3′-end of the DNA spiral, but only MCM6, 4, 7 and 3 make a full set of interactions. DNA binding correlates with nucleotide occupancy: five MCM subunits are bound to either ATPγS or ADP, whereas the apo MCM2-5 interface remains open. We further report the cryoEM structure of human CMG bound to the replisome hub AND-1 (CMGA). The AND-1 trimer uses one β-propeller domain of its trimerisation region to dock onto the side of the helicase assembly formed by Cdc45 and GINS. In the resulting CMGA architecture, the AND-1 trimer is closely positioned to the fork DNA while its CIP (Ctf4-interacting peptide)-binding helical domains remain available to recruit partner proteins.

CryoEM structures of human CMG - ATPγS - DNA and CMG - AND-1 complexes

DNA unwinding in eukaryotic replication is performed by the Cdc45-MCM-GINS (CMG) helicase. Although the CMG architecture has been elucidated, its mechanism of DNA unwinding and replisome interactions remain poorly understood. Here we report the cryoEM structure at 3.3 Å of human CMG bound to fork DNA and the ATP-analogue ATPγS. Eleven nucleotides of single-stranded (ss) DNA are bound within the C-tier of MCM2-7 AAA+ ATPase domains. All MCM subunits contact DNA, from MCM2 at the 5′-end to MCM5 at the 3′-end of the DNA spiral, but only MCM6, 4, 7 and 3 make a full set of interactions. DNA binding correlates with nucleotide occupancy: five MCM subunits are bound to either ATPγS or ADP, whereas the apo MCM2-5 interface remains open. We further report the cryoEM structure of human CMG bound to the replisome hub AND-1 (CMGA). The AND-1 trimer uses one β-propeller domain of its trimerisation region to dock onto the side of the helicase assembly formed by Cdc45 and GINS. In the resulting CMGA architecture, the AND-1 trimer is closely positioned to the fork DNA while its CIP (Ctf4-interacting peptide)-binding helical domains remain available to recruit partner proteins.

The need for the application of modern chemical insecticides and environmental consequences of their use: a mini review

Currently, the use of insecticides is an acute problem. Due to rapid population growth, the primary task is to increase food production. Beyond abiotic factors (drought, soil salinity, etc.) that reduce crop yields, farmers face problems with insect pests that can decrease crop productivity up to 60%. Also, insects are carriers of severe viral and protozoan human diseases. The need for application of insecticides is not questioned but many of them cause resistance of insect pests to them. This, in turn, leads to the necessity to invent new insecticides that are safe and more effective for long-term use. Preparations based on conservative parts of nucleic acids, particularly contact DNA insecticides, could be used to solve insecticide resistance problem as control agents which are well-tailored to target insect pests. This mini review is devoted to these issues.

Differential Gene Regulation by Selective Association of Transcriptional Coactivators and bZIP DNA-Binding Domains

ABSTRACT bZIP DNA-binding domains are targets for viral and cellular proteins that function as transcriptional coactivators. Here, we show that MBF1 and the related Chameau and HBO1 histone acetylases interact with distinct subgroups of bZIP proteins, whereas pX does not discriminate. Selectivity of Chameau and MBF1 for bZIP proteins is mediated by residues in the basic region that lie on the opposite surface from residues that contact DNA. Chameau functions as a specific coactivator for the AP-1 class of bZIP proteins via two arginine residues. A conserved glutamic acid/glutamine in the linker region underlies MBF1 specificity for a subgroup of bZIP factors. Chameau and MBF1 cannot synergistically coactivate transcription due to competitive interactions with the basic region, but either protein can synergistically coactivate with pX. Analysis of Jun derivatives that selectively interact with these coactivators reveals that MBF1 is crucial for the response to oxidative stress, whereas Chameau is important for the response to chemical and osmotic stress. Thus, the bZIP domain mediates selective interactions with coactivators and hence differential regulation of gene expression.

Recognition of Overlapping Nucleotides by AraC and the Sigma Subunit of RNA Polymerase

ABSTRACT The Escherichia coli promoterpBAD , under the control of the AraC protein, drives the expression of mRNA encoding the AraB, AraA, and AraD gene products of the arabinose operon. The binding site of AraC atpBAD overlaps the RNA polymerase −35 recognition region by 4 bases, leaving 2 bases of the region not contacted by AraC. This overlap raises the question of whether AraC substitutes for the sigma subunit of RNA polymerase in recognition of the −35 region or whether both AraC and sigma make important contacts with the DNA in the −35 region. If sigma does not contact DNA near the −35 region, pBAD activity should be independent of the identity of the bases in the hexamer region that are not contacted by AraC. We have examined this issue in thepBAD promoter and in a second promoter where the AraC binding site overlaps the −35 region by only 2 bases. In both cases promoter activity is sensitive to changes in bases not contacted by AraC, showing that despite the overlap, sigma does read DNA in the −35 region. Since sigma and AraC are thus closely positioned atpBAD , it is possible that AraC and sigma contact one another during transcription initiation. DNA migration retardation assays, however, showed that there exists only a slight degree of DNA binding cooperativity between AraC and sigma, thus suggesting either that the normal interactions between AraC and sigma are weak or that the presence of the entire RNA polymerase is necessary for significant interaction.