Sequence Specificity of BAL 31 Nuclease for ssDNA Revealed by Synthetic Oligomer Substrates Containing Homopolymeric Guanine Tracts

Background: The extracellular nuclease from Alteromonas espejiana, BAL 31 catalyzes the degradation of single-stranded and linear duplex DNA to 59-mononucleotides, cleaves negatively supercoiled DNA to the linear duplex form, and cleaves duplex DNA in response to the presence of apurinic sites. Principal Findings: In this work we demonstrate that BAL 31 activity is affected by the presence of guanine in singlestranded DNA oligomers. Specifically, nuclease activity is shown to be affected by guanine’s presence in minimal homopolymeric tracts in the middle of short oligomer substrates and also by its presence at the 39 end of ten and twenty base oligomers. GNC rich regions in dsDNA are known to cause a decrease in the enzyme’s nuclease activity which has been attributed to the increased thermal stability of these regions, thus making it more difficult to unwind the strands required for enzyme access. Our results indicate that an additional phenomenon could be wholly or partly responsible for the loss of activity in these GNC rich regions. Thus the presence of a guanine tract per se impairs the enzyme’s functionality, possibly due to the tract’s bulky nature and preventing efficient progression through the active site. Conclusions: This study has revealed that the general purpose BAL 31 nuclease commonly used in molecular genetics exhibits a hithertofore non-characterized degree of substrate specificity with respect to single-stranded DNA (ssDNA

Sexual Relationships in Hispanic Countries: a Literature Review

This is a pre-print of an article published in Current Sexual Health Reports. The final authenticated version is available online at: https://doi.org/10.1007/s11930-020-00272-6Purpose of Review: Sexuality is a complex dimension for which culture seems to play an important role, particularly in countries that are more traditional. This review summarizes the knowledge about sexual relationships in Hispanic countries, considering sexual debut, attitudes, behaviors, and satisfaction. Recent Findings: In line with the literature reviewed, the sexual double standard seems to be continuing to influence sexual relationships. Some countries show more open expressions of sexuality based on the level of gender inequality or sexualized context, and within countries, variables such as religious commitment, family characteristics, and access to resources may play important roles in sexuality. Summary: Future research, policies, and interventions should consider these specific characteristics, including these forms of expression of sexuality, in the adjustment of cross-cultural and cross-national strategies

Evaluation of a Partial Genome Screening of Two Asthma Susceptibility Regions Using Bayesian Network Based Bayesian Multilevel Analysis of Relevance

Genetic studies indicate high number of potential factors related to asthma. Based on earlier linkage analyses we selected the 11q13 and 14q22 asthma susceptibility regions, for which we designed a partial genome screening study using 145 SNPs in 1201 individuals (436 asthmatic children and 765 controls). The results were evaluated with traditional frequentist methods and we applied a new statistical method, called Bayesian network based Bayesian multilevel analysis of relevance (BN-BMLA). This method uses Bayesian network representation to provide detailed characterization of the relevance of factors, such as joint significance, the type of dependency, and multi-target aspects. We estimated posteriors for these relations within the Bayesian statistical framework, in order to estimate the posteriors whether a variable is directly relevant or its association is only mediated. With frequentist methods one SNP (rs3751464 in the FRMD6 gene) provided evidence for an association with asthma (OR = 1.43(1.2–1.8); p = 3×10−4). The possible role of the FRMD6 gene in asthma was also confirmed in an animal model and human asthmatics. In the BN-BMLA analysis altogether 5 SNPs in 4 genes were found relevant in connection with asthma phenotype: PRPF19 on chromosome 11, and FRMD6, PTGER2 and PTGDR on chromosome 14. In a subsequent step a partial dataset containing rhinitis and further clinical parameters was used, which allowed the analysis of relevance of SNPs for asthma and multiple targets. These analyses suggested that SNPs in the AHNAK and MS4A2 genes were indirectly associated with asthma. This paper indicates that BN-BMLA explores the relevant factors more comprehensively than traditional statistical methods and extends the scope of strong relevance based methods to include partial relevance, global characterization of relevance and multi-target relevance

Mismatch repair participates in error-free processing of DNA interstrand crosslinks in human cells

DNA interstrand crosslinks (ICLs) present formidable blocks to DNA metabolic processes and must be repaired for cell survival. ICLs are induced in DNA by intercalating compounds such as the widely used therapeutic agent psoralen. In bacteria, both nucleotide excision repair (NER) and homologous recombination are required for the repair of ICLs. The processing of ICLs in mammalian cells is not clearly understood. However, it is known that processing can occur by NER, which for psoralen ICLs can be an error-generating process conducive to mutagenesis. We show here that another repair pathway, mismatch repair (MMR), is also involved in eliminating psoralen ICLs in human cells. MMR deficiency renders cells hypersensitive to psoralen ICLs without diminishing their mutagenic potential, suggesting that MMR does not contribute to error-generating repair, and that MMR may represent a relatively error-free mechanism for processing these lesions in human cells. Thus, enhancement of MMR relative to NER may reduce the mutagenesis caused by DNA ICLs in humans

Replication-coupled DNA interstrand cross-link repair in Xenopus egg extracts

Interstrand cross-links (ICL) are one of the most hazardous types of DNA damage as they form a roadblock to all processes that involve strand separation. Repair of these lesions involves several different DNA repair pathways, but the molecular mechanism is unclear. Here we describe a system that allows the examination of ICL repair, via a physiological mechanism, in vitro. This system, which uses Xenopus egg extracts in combination with a DNA template that contains a site-specific ICL, represents a unique tool to study the molecular mechanism of ICL repair