Nature and intensity of selection pressure on CRISPR-associated genes

The recently discovered CRISPR-Cas adaptive immune system is present in almost all archaea and many bacteria. It consists of cassettes of CRISPR repeats that incorporate spacers homologous to fragments of viral or plasmid genomes that are employed as guide RNAs in the immune response, along with numerous CRISPR-associated (cas) genes that encode proteins possessing diverse, only partially characterized activities required for the action of the system. Here, we investigate the evolution of the cas genes and show that they evolve under purifying selection that is typically much weaker than the median strength of purifying selection affecting genes in the respective genomes. The exceptions are the cas1 and cas2 genes that typically evolve at levels of purifying selection close to the genomic median. Thus, although these genes are implicated in the acquisition of spacers from alien genomes, they do not appear to be directly involved in an arms race between bacterial and archaeal hosts and infectious agents. These genes might possess functions distinct from and additional to their role in the CRISPR-Cas-mediated immune response. Taken together with evidence of the frequent horizontal transfer of cas genes reported previously and with the wide-spread microscale recombination within these genes detected in this work, these findings reveal the highly dynamic evolution of cas genes. This conclusion is in line with the involvement of CRISPR-Cas in antiviral immunity that is likely to entail a coevolutionary arms race with rapidly evolving viruses. However, we failed to detect evidence of strong positive selection in any of the cas genes.     

Mac-1 promotes FcgammaRIIA-dependent cell spreading and migration on immune complexes

The integrin Mac-1 plays a critical role in Fc receptor (FcR)-mediated antibody-dependent cellular cytotoxicity (ADCC). However, the mechanism by which Mac-1 facilitates the functions of FcgammaRIIA, a major FcR expressed on human leukocytes, is not fully understood. We report here that Mac-1 sustains cell adhesion, enhances cell spreading, and accelerates cell migration on preformed immune complexes (ICs) by directly interacting with FcgammaRIIA but not with the IC substrate. Coupling Mac-1 to FcgammaRIIA allows FcgammaRIIA to reside in the leading front of actin polymerization at the filopodial extension and thus could potentially enhance FcgammaRIIA-mediated cell spreading and migration. The direct interaction between Mac-1 and FcgammaRIIA is demonstrated by co-immunoprecipitation, by cell surface co-localization, and by solid-phase binding assays using recombinant alpha(M)I-domain and soluble FcgammaRIIA. Further mutational analysis identifies the E(253)-R(261) sequence within the alpha(M)I-domain as part of the FcgammaRIIA binding interface within Mac-1. Altogether, these results demonstrate that FcgammaRIIA recognizes Mac-1 via the alpha(M)I-domain but not the lectin domain, a distinct feature from other FcRs, and that Mac-1 binding confers FcgammaRIIA with the ability to prolong cell adhesion as well as to spread and migrate on the ICs, leading to effective cell killing by ADCC.     

A false note of DNA polymerase iota in the choir of genome caretakers in mammals

DNA polymerase iota (Pol iota) of mammals is a member of the Y family of DNA polymerases. Among many other genome caretakers, these enzymes are responsible for maintaining genome stability. The members of the Y-family DNA polymerases take part in translesion DNA synthesis, bypassing some DNA lesions, and are characterized by low fidelity of DNA synthesis. A unique ability of Pol iota to predominantly incorporate G opposite T allowed us to identify the product of this enzyme among those synthesized by other DNA polymerases. This product can be called a "false note" of Pol iota. We measured the enzyme activity of Pol iota in crude extracts of cells from different organs of five inbred strains of mice (N3H/Sn, 101/H, C57BL/6, BALB/c, 129/J) that differed in a number of parameters. The "false note" of Pol iota was clearly sounding only in the extracts of testis and brain cells from four analyzed strains: N3H/Sn, 101/H, C57BL/6, BALB/c. In mice of 129/J strain that had a nonsense mutation in the second exon of the pol iota gene, the Pol iota activity was reliably detectable only in the extracts of brain. The data show that the active enzyme can be formed in some cell types even if they carry a nonsense mutation in the pol iota gene. This supports tissue-specific regulation of pol iota gene expression through alternative splicing. A semiquantitative determination of pol iota activity in mice strains different in their radiosensitivity suggests a reciprocal correlation between the enzyme activity of pol iota in testis and the resistance of mice to radiation.     

Morphofunctional characterization of mast cells of the skin and the mucous membrane of airways in specific hyposensitization carried out on an experimental model

The study of the morphofunctional state of the population of guinea-pig mast cells in response to the action of specific allergen was carried out. The mast cells of different guinea pigs, intact and sensitized, as well as those hyposensitized by two methods, the classical method and the method combining extracorporeal and oro- pharyngeal hyposensitization, were compared. As shown in this study, after specific hyposensization the tendency towards the normalization of the morphofunctional state of the mast-cell population in the airway walls and the skin was noted.     

The effect of the background color of computer programs on the functional state of preschool children working on a computer

The effect of work on a computer on the functional state of preschool children (five to six years of age) using developing software (DS) with differently colored backgrounds (lettuce green, blue, black, or graypurple) has been studied. All other characteristics of DS were alike: the same children were examined while working with each of the four experimental DS. Different methods were used for processing and analysis of 240 to 1920 measurements. Only the lettuce green background proved to be adequate for five- to six-tear-old children: eight out of the nine tested indices of the functional state of preschool children showed a favorable tendency from the beginning to the end of the work. On the contrary, most indices after the work of children with DS on the blue, black, and gray-purple backgrounds (six, nine, and nine out of nine indices, respectively) were significantly impaired; impairment of the functional state of the central nervous system was detected in 14–25% of cases; general mental fatigue was observed in many cases (31–40%); and visual fatigue was found in 16–25% of cases.     

Comprehensive comparative-genomic analysis of Type 2 toxin-antitoxin systems and related mobile stress response systems in prokaryotes

Background  

The prokaryotic toxin-antitoxin systems (TAS, also referred to as TA loci) are widespread, mobile two-gene modules that can be viewed as selfish genetic elements because they evolved mechanisms to become addictive for replicons and cells in which they reside, but also possess "normal" cellular functions in various forms of stress response and management of prokaryotic population. Several distinct TAS of type 1, where the toxin is a protein and the antitoxin is an antisense RNA, and numerous, unrelated TAS of type 2, in which both the toxin and the antitoxin are proteins, have been experimentally characterized, and it is suspected that many more remain to be identified.     

Analysis of the N-acetyltransferase 2 gene polymorphism in the patients with chronic obstructive pulmonary disease and in populations of the Volga-Ural region

Restriction fragment-length polymorphism of the gene coding for N-acetyltransferase 2 (NAT2) was typed in populations of the Volga-Ural region (Bashkirs, Tatars, Chuvashes, Udmurts, and Russians) as well as in patients with chronic obstructive pulmonary disease (COPD) and in healthy individuals. Rapid and slow acetylator phenotypes were determined based on the presence or absence of the KpnI, TaqI, and BamHI restriction endonuclease recognition sites. The proportion of slow acetylators in the populations examined varied from 40.00% in Bashkirs to 64.15% in Chuvashes with statistically significant difference between these two ethnic groups (chi 2 = 5.7; p = 0.02). Overall, in the Volga-Ural populations slow acetylators represented 56.25% of the subjects examined. This value was similar to those presented in other studies of Caucasoid populations. In the COPD patients a statistically significant decrease of the slow acetylator frequency to 48.28% compared to healthy individuals (62.18%) was observed (chi 2 = 4.60; p = 0.036). The data obtained suggest a possible association between the drug resistance in the COPD patients with the rapid acetylator phenotype, which can lead to the development of the chronic form of the disease.