Disintegration promotes protospacer integration by the Cas1-Cas2 complex

‘Disintegration’—the reversal of transposon DNA integration at a target site—is regarded as an abortive off-pathway reaction. Here, we challenge this view with a biochemical investigation of the mechanism of protospacer insertion, which is mechanistically analogous to DNA transposition, by the Streptococcus pyogenes Cas1-Cas2 complex. In supercoiled target sites, the predominant outcome is the disintegration of one-ended insertions that fail to complete the second integration event. In linear target sites, one-ended insertions far outnumber complete protospacer insertions. The second insertion event is most often accompanied by the disintegration of the first, mediated either by the 3′-hydroxyl exposed during integration or by water. One-ended integration intermediates may mature into complete spacer insertions via DNA repair pathways that are also involved in transposon mobility. We propose that disintegration-promoted integration is functionally important in the adaptive phase of CRISPR-mediated bacterial immunity, and perhaps in other analogous transposition reactions.

Disintegration promotes proto-spacer integration by the Cas1-Cas2 complex

Abstract‘Disintegration’—the reversal of transposon DNA integration at a target site—is regarded as an abortive off-pathway reaction. Here we challenge this view with a biochemical investigation of the mechanism of protospacer insertion by the Streptococcus pyogenes Cas1-Cas2 complex, which is mechanistically analogous to DNA transposition. In supercoiled target sites, the predominant outcome is the disintegration of one-ended insertions that fail to complete the second integration event. In linear target sites, one-ended insertions far outnumber complete proto-spacer insertions. The second insertion event is most often accompanied by disintegration of the first, mediated either by the 3’-hydroxyl exposed during integration or by water. One-ended integration intermediates may mature into complete spacer insertions via DNA repair pathways that are also involved in transposon mobility. We propose that disintegration-promoted integration is functionally important in the adaptive phase of CRISPR-mediated bacterial immunity, and perhaps in other analogous transposition reactions.

Computer support services of contamination threats analysis and alarming in WAZkA system for Polish KSWSiA

The article outlines a concept for the system supporting analyses of threats related to contamination and alarming (WAZkA), for the purpose of the National System for Detection of Contamination and Alarming (Krajowy System Wykrywania Skażeń i Alarmowania, KSWSiA) in Poland. The selected modules included in the WAZkA system: Event Tree Analyzer, visualization module and emulators of the threats monitoring systems, were described as well as the idea of using the system for the purpose of training, including the designed emulators of the risk monitoring systems together with the scenario editor. Keywords: CBRN threats, contamination hazard analysis and alerting support system, CBRN threats monitoring systems integration, alerting and warning systems integration, event trees

A Single Banana Streak Virus Integration Event in the Banana Genome as the Origin of Infectious Endogenous Pararetrovirus

ABSTRACTSequencing of plant nuclear genomes reveals the widespread presence of integrated viral sequences known as endogenous pararetroviruses (EPRVs). Banana is one of the three plant species known to harbor infectious EPRVs.Musa balbisianacarries integrated copies ofBanana streak virus(BSV), which are infectious by releasing virions in interspecific hybrids. Here, we analyze the organization of the EPRV of BSV Goldfinger (BSGfV) present in the wild diploidM. balbisianacv. Pisang Klutuk Wulung (PKW) revealed by the study ofMusabacterial artificial chromosome resources and interspecific genetic cross. cv. PKW contains two similar EPRVs of BSGfV. Genotyping of these integrants and studies of their segregation pattern show an allelic insertion. Despite the fact that integrated BSGfV has undergone extensive rearrangement, both EPRVs contain the full-length viral genome. The high degree of sequence conservation between the integrated and episomal form of the virus indicates a recent integration event; however, only one allele is infectious. Analysis of BSGfV EPRV segregation among an F1 population from an interspecific genetic cross revealed that these EPRV sequences correspond to two alleles originating from a single integration event. We describe here for the first time the full genomic and genetic organization of the two EPRVs of BSGfV present in cv. PKW in response to the challenge facing both scientists and breeders to identify and generate genetic resources free from BSV. We discuss the consequences of this unique host-pathogen interaction in terms of genetic and genomic plant defenses versus strategies of infectious BSGfV EPRVs.