Functional Characteristics of a Highly Specific Integrase Encoded by an LTR-Retrotransposon

Background: The retroviral Integrase protein catalyzes the insertion of linear viral DNA into host cell DNA. Although different retroviruses have been shown to target distinctive chromosomal regions, few of them display a site-specific integration. ZAM, a retroelement from Drosophila melanogaster very similar in structure and replication cycle to mammalian retroviruses is highly site-specific. Indeed, ZAM copies target the genomic 59-CGCGCg-39 consensus-sequences. To enlighten the determinants of this high integration specificity, we investigated the functional properties of its integrase protein denoted ZAM-IN. Principal Findings: Here we show that ZAM-IN displays the property to nick DNA molecules in vitro. This endonuclease activity targets specific sequences that are present in a 388 bp fragment taken from the white locus and known to be a genomic ZAM integration site in vivo. Furthermore, ZAM-IN displays the unusual property to directly bind specific genomic DNA sequences. Two specific and independent sites are recognized within the 388 bp fragment of the white locus: the CGCGCg sequence and a closely apposed site different in sequence. Conclusion: This study strongly argues that the intrinsic properties of ZAM-IN, ie its binding properties and its endonuclease activity, play an important part in ZAM integration specificity. Its ability to select two binding sites and to nick the DNA molecule reminds the strategy used by some site-specific recombination enzymes and forms the basis for site-specifi

Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, and the International Standard ISO 23162:2021. With these tools, we propose that authors should be instructed to follow these laboratory methods in order to publish studies in peer-reviewed journals, preferable by using a checklist as suggested in an Appendix to this article

Methodological issues in defining aggression for content analyses of sexually explicit material

There exists an important tradition of content analyses of aggression in sexually explicit material. The majority of these analyses use a definition of aggression that excludes consent. This article identifies three problems with this approach. First, it does not distinguish between aggression and some positive acts. Second, it excludes a key element of healthy sexuality. Third, it can lead to heteronormative definitions of healthy sexuality. It would be better to use a definition of aggression such as Baron and Richardson's (1994) in our content analyses, that includes a consideration of consent. A number of difficulties have been identified with attending to consent but this article offers solutions to each of these