ASSESSMENT OF REASONS FOR THE TERMINATION ACTIVITY OF ENTREPRENEURS IN MODERN ECONOMIES

Every entrepreneur sooner or later ceases their activities. At the same time, little attention is paid to this stage of the life cycle of entrepreneurs in scientific research. Proper understanding of the reasons for the exit of entrepreneurs from business is necessary for the further development of the business sector. Therefore, the analysis of features of termination of business activity in national economies is relevant at the present stage of research. Purpose of the study is to assess the reasons for the exit of entrepreneurs from their own business. The study used information from the 2018 global entrepreneurship monitor for 48 countries. We have studied and analyzed the reasons for the termination of entrepreneurial activity, proposed a classification of these reasons, assessed the levels of exit from their own business for different groups of reasons in all the countries considered. This estimate was based on the construction of economic-mathematical models. Models are functions of the density of the normal distribution. Based on the results of the computational experiment, the average values of indicators were determined and the countries characterized by high and low levels of termination of their activities by entrepreneurs were identified. It is proved that in most countries the termination of business activity is caused by endogenous reasons associated with problems in the organization and management of production, insufficient financial resources, low qualification of employees and management. Personal reasons also play a significant role in the exit of entrepreneurs. The impact of exogenous causes and the desire to convert the created business into cash is much lower. The obtained research results can be used in further studies, in the educational process of higher education in universities, as well as by public authorities associated with the regulation of entrepreneurial activity.

Two classes of EF1-family translational GTPases encoded by giant viruses

Giant viruses have extraordinarily large dsDNA genomes, and exceptionally, they encode various components of the translation apparatus, including tRNAs, aminoacyl-tRNA synthetases and translation factors. Here, we focused on the elongation factor 1 (EF1) family of viral translational GTPases (trGTPases), using computational and functional approaches to shed light on their functions. Multiple sequence alignment indicated that these trGTPases clustered into two groups epitomized by members of Mimiviridae and Marseilleviridae, respectively. trGTPases in the first group were more closely related to GTP-binding protein 1 (GTPBP1), whereas trGTPases in the second group were closer to eEF1A, eRF3 and Hbs1. Functional characterization of representative GTPBP1-like trGTPases (encoded by Hirudovirus, Catovirus and Moumouvirus) using in vitro reconstitution revealed that they possess eEF1A-like activity and can deliver cognate aa-tRNAs to the ribosomal A site during translation elongation. By contrast, representative eEF1A/eRF3/Hbs1-like viral trGTPases, encoded by Marseillevirus and Lausannevirus, have eRF3-like termination activity and stimulate peptide release by eRF1. Our analysis identified specific aspects of the functioning of these viral trGTPases with eRF1 of human, amoebal and Marseillevirus origin.

Factor-dependent archaeal transcription termination

RNA polymerase activity is regulated by nascent RNA sequences, DNA template sequences, and conserved transcription factors. Transcription factors promoting initiation and elongation have been characterized in each domain, but transcription termination factors have been identified only in bacteria and eukarya. Here we describe euryarchaeal termination activity (Eta), the first archaeal termination factor capable of disrupting the transcription elongation complex (TEC), detail the rate of and requirements for Eta-mediated transcription termination, and describe a role for Eta in transcription termination in vivo. Eta-mediated transcription termination is energy-dependent, requires upstream DNA sequences, and disrupts TECs to release the nascent RNA to solution. Deletion of TK0566 (encoding Eta) is possible, but results in slow growth and renders cells sensitive to DNA damaging agents. Our results suggest that the mechanisms used by termination factors in archaea, eukarya, and bacteria to disrupt the TEC may be conserved, and that Eta stimulates release of stalled or arrested TECs.

Methylation of Bacterial Release Factors RF1 and RF2 Is Required for Normal Translation Termination in Vivo

Bacterial release factors RF1 and RF2 are methylated on the Gln residue of a universally conserved tripeptide motif GGQ, which interacts with the peptidyl transferase center of the large ribosomal subunit, triggering hydrolysis of the ester bond in peptidyl-tRNA and releasing the newly synthesized polypeptide from the ribosome. In vitro experiments have shown that the activity of RF2 is stimulated by Gln methylation. The viability of Escherichia coli K12 strains depends on the integrity of the release factor methyltransferase PrmC, because K12 strains are partially deficient in RF2 activity due to the presence of a Thr residue at position 246 instead of Ala. Here, we study in vivo RF1 and RF2 activity at termination codons in competition with programmed frameshifting and the effect of the Ala-246 → Thr mutation. PrmC inactivation reduces the specific termination activity of RF1 and RF2(Ala-246) by ∼3- to 4-fold. The mutation Ala-246 → Thr in RF2 reduces the termination activity in cells ∼5-fold. After correction for the decrease in level of RF2 due to the autocontrol of RF2 synthesis, the mutation Ala-246 → Thr reduced RF2 termination activity by ∼10-fold at UGA codons and UAA codons. PrmC inactivation had no effect on cell growth in rich media but reduced growth considerably on poor carbon sources. This suggests that the expression of some genes needed for optimal growth under such conditions can become growth limiting as a result of inefficient translation termination.

Role of CIS in Replication of an IncB Plasmid

ABSTRACT Replication of the IncB plasmid pMU720 requires the synthesis of the cis-acting RepA protein and the presence of two DNA elements, ori and CIS. CIS is the 166-bp sequence separating the RepA coding sequence from ori. To investigate how this organization of the pMU720 replicon contributes to the mechanism of initiation of replication, mutations in the sequence and/or the length of CIS were introduced into theCIS region and their effects on the efficiency of replication of the pMU720 replicon in vivo was determined. TheCIS region was found to be composed of two domains. TherepA-proximal domain, which showed strong transcription termination activity, could be replaced by equivalent sequences from I-complex and IncL/M plasmids, whose replicons are organized in the same fashion as pMU720. Replacement by a trpA transcription terminator afforded only partial replication activity. TherepA-distal domain was shown to be a spacer whose role was to position sequence(s) within ori on the correct face of the DNA helix vis-à-vis the repA-proximal portion ofCIS. A model for the loading of RepA protein ontoori is discussed.

Transcription termination signals in the nin region of bacteriophage lambda: identification of Rho-dependent termination regions.

The approximately 3-kb nin region of bacteriophage lambda, located between genes P and Q contains transcription termination signals as well as 10 open reading frames. Deletions in the nin region frees phage growth from dependence on the lambda-encoded N-transcription antitermination system, conferring a Nin phenotype (N-independence). A subregion of nin, roc, is defined by a 1.9-kb deletion (delta roc) which partially frees lambda growth from the requirement for N antitermination. The roc region has strong transcription termination activity as assayed by a plasmid-based terminator testing system. We report the following features of the roc region: the biologically significant terminators in the roc region are Rho dependent, deletion analysis located the biologically significant termination signals to a 1.2 kb-segment of roc, and analysis of other deletions and point mutations in the roc region suggested at least two biologically significant regions of termination, tR3 (extending from bp 42020 to 42231) and tR4 (extending from bp 42630 to 42825).