Integration of DNA copies in a host genome is a necessary stage in the life cycle of retroviruses and LTR-retrotransposons. There is still no clear understanding of integration specificity of retroelements into a target site. The selection of the target DNA is believed to potentially affect a number of factors such as transcriptional status, association with histones and other DNA-binding proteins, and DNA bending. The authors performed a comprehensive computer analysis of the integration specificity of Drosophila melanogaster LTR-retrotransposons and retroviruses including an analysis of the nucleotide composition of targets, terminal sequences of LTRs, and integrase sequences. A classification of LTR-retrotransposons based on the integration specificity was developed. All the LTR-retrotransposons of the gypsy group with three open frames (errantiviruses) and their derivatives with two open frames demonstrate strict specificity to a target DNA selection. Such specificity correlates with the structural features of the target DNA: bendability, A-philicity, or protein-induced deformability. The remaining LTR-retrotransposons (copia and BEL groups, blastopia and 412 subgroups of the gypsy group) do not show specificity of integration. Chromodomain is present in the integrase structures of blastopia and 412 subgroup LTR-retrotransposons and may facilitate the process of non-specific integration.
The domestication of foreign genes is a powerful mechanism for new gene formation and genome evolution. It is known that domesticated retroviral gag genes in mammals not only take part in protecting against viral infection but also control cell division, apoptosis, function of the placenta, and other biological processes. In this study, we focused on the domesticated retroviral gag gene homolog (Grp) in the Drosophila melanogaster genome. According to the results of a bioinformatic analysis, the Grp gene product is primarily under purifying selection in Drosophilidae family. The Grp protein has been shown to be transmembrane. The Grp gene is expressed at the adult stage of D. melanogaster in gender-specific and tissue-specific manner. Also the Grp gene expression is increased in response to the gypsy retrovirus. A function of the protein as a component of the endosomic membrane is considered.
Long terminal repeat (LTR) retrotransposons occupy a special place among all mobile genetic element families. The structure of LTR retrotransposons that have three open reading frames is identical to DNA forms of retroviruses that are integrated into the host genome. Several lines of evidence suggest that LTR retrotransposons share a common ancestry with retroviruses and thus are highly relevant to understanding mechanisms of transposition. Drosophila melanogaster is an exceptionally convenient model for studying the mechanisms of retrotransposon movement because many such elements in its genome are transpositionally active. Moreover, two LTR-retrotransposons of D. melanogaster, gypsy and ZAM, have been found to have infectious properties and have been classified as errantiviruses. Despite numerous studies focusing on retroviral integration process, there is still no clear understanding of integration specificity in a target site. Most LTR retrotransposons non-specifically integrate into a target site. Site-specificity of integration at vertebrate retroviruses is rather relative. At the same time, sequence-specific integration is the exclusive property of errantiviruses and their derivatives with two open reading frames. The possible basis for the errantivirus integration specificity is discussed in the present review.
Физиологическое действие гипоталамо-гипо-физарно-гонадной оси основывается на пульсиру-ющей гипоталамической секреции гонадолиберина (ГнРГ), нарушение которой является причиной ред-ких заболеваний, объединяемых под термином ги-погонадизм. Отсутствие ГнРГ приводит к дезакти-вации рецептора на поверхности гонадотрофов аде-ногипофиза и выпадению стимулирующего дей-ствия на синтез и высвобождение гонадотропинов (ЛГ и ФСГ) в общий кровоток. Дефицит ЛГ и ФСГ обусловливает отсутствие гаметогенеза и синтеза половых стероидов. Таким образом, нормальное функционирование репродуктивной системы зави-сит от скоординированной работы трех звеньев: ар-куатных ядер гипоталамуса, гонадотрофов гипофиза и гонад (рис. 1).В зависимости от сроков возникновения разли-чают врожденный и приобретенный гипогонадизм, а в зависимости от уровня поражения -первичный (поражение самих гонад) и вторичный (гипоталамо-гипофизарный) гипогонадизм. Существует также классификация, разделяющая поражения гипофиза и гипоталамуса на вторичный и третичный уровень
Drosophila melanogaster is one of the most extensively used genetic model organisms for studying LTR retrotransposons that are represented by various groups in its genome. However, the phenomenon of molecular domestication of LTR retrotransposons has been insufficiently studied in Drosophila, as well as in other invertebrates. The present work is devoted to studying the role of the domesticated gag gene, Gagr, in the Drosophila genome. The Gagr gene has been shown to be involved in the response to stress caused by exposure to ammonium persulfate, but not in the stress response to oligomycin A, zeomycin, and cadmium chloride. Ammonium persulfate tissue specifically activates the expression of Gagr in the tissues of the carcass, but not in the gut. We found that the Gagr gene promoter contains one binding motif for the transcription factor kayak, a component of the JNK signaling pathway, and two binding motifs for the transcription factor Stat92E, a component of the Jak-STAT signaling pathway. Remarkably, Gagr orthologs contain the second binding motif for Stat92E only in D. melanogaster, D. simulans and D. sechellia, whereas in D. yakuba and D. erecta, Gagr orthologs contain a single motif, and there are no binding sites for Stat92E in the promoters of Gagr orthologs in D. ananassae and in species outside the melanogaster group. The data obtained indicate the formation of the protective function of the Gagr gene during evolution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.