Explore the vast range of titles available.

Background Short interspersed elements (SINEs) are non-autonomous retroelements that are transcribed by RNA polymerase III from an internal promoter. Most SINE families originate from tRNAs, but a few, exclusively within supraprimates (primates, rodents, tree shrews) and, exceptionally, hagfish, derive from the 7SL RNA. These 7SL-derived SINEs all arose after an ~ 183-nt central deletion in the 7SL RNA sequence and are mobilized by LINE1-encoded reverse transcriptase. No 7SL-derived SINE has previously been reported outside these taxa. Results Mining of mole (Talpidae) genomes revealed no mole-specific tRNA-derived SINE in the gracile shrew mole Uropsilus gracilis . Instead, ~ 280 000 copies of a dimeric 7SL RNA-derived SINE, named Urop, populate its genome but not five other talpid species. Three subfamilies (a–c) share two 7SL-derived monomers joined by an A-rich linker. The left monomer and Urop_a right monomer carry the canonical central deletion; Urop_b/c right monomers additionally harbor a 24-nt tandem duplication, paralleling the 29-nt quasi-dimer of murid B1. Monomeric fossils suggest they preceded dimeric Urop formation. Sequence divergence and subfamily analysis date the origin of Urop soon after the Uropsilinae split from other moles. Urop_c, the youngest subfamily, displays a striking excess of extra-long pure poly(A) tails, far exceeding those in young human AluY elements. Conclusions Urop represents a remarkable case of convergent evolution, independently generating an Alu-like dimeric SINE in a distantly related mammal. Its independent origin from 7SL RNA, parallel structural trajectory (monomer → dimer via identical deletion boundaries), and suppression of tRNA-derived SINEs mirror the evolutionary history of primate Alu. The abundance of long intact poly(A) tails in Urop_c suggests unique biochemical controls on tail dynamics and hint at continued retropositional activity. These findings underscore the exceptional evolutionary potential of rare, large-scale deletions within 7SL RNA as a SINE progenitor and raises new questions about poly(A) tail regulation and SINE family dynamics.

Background Leishmaniasis is endemic in Tunisia and presents with different clinical forms, caused by the species Leishmania infantum , Leishmania major , and Leishmania tropica . The life cycle of Leishmania is complex and involves several phlebotomine sand fly vectors and mammalian reservoir hosts. The aim of this work is the development and evaluation of a high-resolution melting PCR (PCR-HRM) tool to detect and identify Leishmania parasites in wild and domestic hosts, constituting confirmed (dogs and Meriones rodents) or potential (hedgehogs) reservoirs in Tunisia. Methods Using in vitro-cultured Leishmania isolates, PCR-HRM reactions were developed targeting the 7SL RNA and HSP70 genes. Animals were captured or sampled in El Kef Governorate, North West Tunisia. DNA was extracted from the liver, spleen, kidney, and heart from hedgehogs ( Atelerix algirus ) ( n  = 3) and rodents ( Meriones shawi ) ( n  = 7) and from whole blood of dogs ( n  = 12) that did not present any symptoms of canine leishmaniasis. In total, 52 DNA samples were processed by PCR-HRM using both pairs of primers. Results The results showed melting curves enabling discrimination of the three Leishmania species present in Tunisia, and were further confirmed by Sanger sequencing. Application of PCR-HRM assays on reservoir host samples showed that overall among the examined samples, 45 were positive, while seven were negative, with no Leishmania infection. Meriones shawi were found infected with L. major , while dogs were infected with L. infantum . However, co-infections with L. major / L. infantum species were detected in four Meriones specimens and in all tested hedgehogs. In addition, multiple infections with the three Leishmania species were found in one hedgehog specimen. Sequence analyses of PCR-HRM products corroborated the Leishmania species found in analyzed samples. Conclusions The results of PCR-HRM assays applied to field specimens further support the possibility of hedgehogs as reservoir hosts of Leishmania . In addition, we showed their usefulness in the diagnosis of canine leishmaniasis, specifically in asymptomatic dogs, which will ensure a better evaluation of infection extent, thus improving elaboration of control programs. This PCR-HRM method is a robust and reliable tool for molecular detection and identification of Leishmania and can be easily implemented in epidemiological surveys in endemic regions. Graphical Abstract

Backgrounds: Mutation of protein-coding genes and non-coding genes is a factor in psoriasis etiology. Non-coding RNA (ncRNA), which does not have protein-coding capacity, is available in the human genome. HOTAIR (HOX Antisense Intergenic RNA) and 7SL-RNA are known as ncRNA. They may play a role in psoriasis pathogenesis. Aims: In our study, we aimed to investigate the level of HOTAIR and 7SL-RNA gene expression in the lesional and perilesional healthy skin of psoriasis patients. Methods: Total RNA isolation from the skin samples was achieved by modifying the RNeasy Mini Kit (Qiagen, Cat No: 74104) protocol. Real Time Polymerase Chain Reaction (qPCR) phase was performed in accordance with the protocol of the relevant brand (WizPure qPCR). Results: 7SL-RNA gene expression decreased in the skin with psoriatic lesions (FC: 0.01; p: 0.028), and this decrease was statistically significant. HOTAIR gene expression decreased (FC: 0.92; p: 0.218), but this decrease was not statistically significant. Conclusions: lncRNAs may play a role in the pathogenesis of psoriasis disease.

The Alu element, the most prevalent SINE (short interspersed element) in the human genome, is one of the many RNA-encoding genes that evolved from the 7SL RNA gene. During analysis of the evolution of 7SL-derived RNAs, two distinct evolutionary intermediates capable of self-catalyzed DNA depurination (SDP) were identified. These SDP sequences spontaneously create apurinic sites that can result in increased mutagenesis due to their error-prone repair. This DNA self-depurination mechanism has been shown both in vitro and in vivo to lead to substitution and short frameshift mutations at a frequency that far exceeds their occurrence due to random errors in DNA replication. In both evolutionary intermediates, the same self-depurination sequence overlaps motifs necessary for successful transcription and SRP9/14 (signal recognition particle) binding; hence, mutations in this region could disrupt RNA activity. Yet, the 7SL-derived RNAs that arose from the elements capable of SDP show significant diversity in this region, and every new sequence retains the transcription and SRP9/14-binding motifs, even as it has lost the SDP sequence. While some (but not all) of the mutagenesis can be alternatively attributed to CpG decay, the very fact that the self-depurinating sequences are selectively discarded in all cases suggests that this was evolutionarily motivated to prevent further destructive mutagenesis by the SDP mechanism.

Leishmania is a group of parasitic protozoa that infect blood and tissue phagocytes including macrophages. We hypothesize that Leishmania is capable of establishing infection inside the macrophages because (a) they infect a subpopulation of macrophages; and (b) they “renovate” the macrophages before the establishment of infection. We found that only alternatively activated polarized M2 macrophages support Leishmania growth. Exposure of M2 macrophages to Leishmania promastigotes represses several selected RNA polymerase III (PolIII)-transcribed non-coding RNA (ncRNA) genes including those of 7SL RNA, vault RNA, and B2 RNA which have B-box element at their promoters. The B-box-binding transcription factor TFIIIC110 is down-regulated in Leishmania-exposed macrophages. Both the surface protease gp63 and the surface glycolipid LPG are required for the down-regulation of the ncRNAs in the M2 macrophages. We conclude that Leishmania surface gp63 collaborates with LPG to down-regulate TFIIIC110 in M2 macrophages to repress B-box containing ncRNA gene promoters.

BACKGROUND: Leishmaniasis is a vector-borne disease, which is still endemic in the west and northwest area of China. Canines are the major reservoirs of Leishmania, the etiological agent of human visceral leishmaniasis. Phlebotomus chinensis is the main transmission vector of zoonotic visceral leishmaniasis (ZVL). METHODS: In this study, rK39 dip-stick, ELISA and PCR methods were used to investigate the prevalence of canine leishmaniasis (CanL) in Beichuan County, Sichuan Province, China. RESULTS: Among the 86 dogs which were included in the study, 13 dogs were positive using the dip-stick test (15.12%), while 8 dogs were positive using ELISA (9.30%) and 19 dogs were positive for PCR (22.03%). In total, 32 dogs were positive for one or more tests (37.21%). Interestingly, phylogenetic analysis based on the partial 7SL RNA fragment provided evidence that an undescribed Leishmania species, which is clearly a causative agent of CanL and human visceral leishmaniasis, does exist in China. This result is consistent with our previous study. CONCLUSIONS: Our work confirmed that canine leishmaniasis is still prevalent in Beichuan County. Further control is urgently needed, as canine leishmaniasis is of great public health importance. The phylogenetic analysis based on 7SL RNA segment provides evidence for the existence of an undescribed Leishmania sp. in China.

We characterized two novel 7SL RNA–derived short interspersed nuclear element (SINE) families (Tu types I and II) and a novel tRNA-derived SINE family (Tu type III) from the tree shrew (Tupaia belangeri). Tu type I contains a monomer unit of a 7SL RNA–derived Alu-like sequence and a tRNA-derived region that includes internal RNA polymerase III promoters. Tu type II has a similar hybrid structure, although the monomer unit of the 7SL RNA–derived sequence is replaced by a dimer. Along with the primate Alu, the galago Alu type II, and the rodent B1, these two families represent the fourth and fifth 7SL RNA–derived SINE families to be identified. Furthermore, comparison of the Alu domains of Tu types I and II with those of other 7SL RNA–derived SINEs reveals that the nucleotides responsible for stabilization of the Alu domain have been conserved during evolution, providing the possibility that these conserved nucleotides play an indispensable role in retropositional activity. Evolutionary relationships among these 7SL RNA–derived SINE families, as well as phylogenetic relationships of their host species, are discussed.

The leishmaniases are zoonotic diseases caused by protozoan parasites of the genus Leishmania . Leishmaniases are still endemic in China, especially in the west and northwest froniter regions. To revalue the preliminary phylogenetic results of Chinese Leishmania isolates, we amplified partial fragment of small subunit ribosomal RNA (SSU rRNA) and 7 spliced leader RNA (7SL RNA), then tested the phylogenetic relationships among Chinese Leishmania isolates and their relatives by analyzing SSU rRNA gene sequences and 7SL RNA gene sequences. 19 SSU RNA sequences and 9 7SL RNA sequences were obtained in our study, then analyzed with 42 SSU RNA sequences and 32 7SL RNA sequences retrieved from Genbank, respectively. In the Bayesian analysis of the SSU RNA gene, the isolate MHOM/CN/93/GS7 and the isolate IPHL/CN/77/XJ771 are members of Leishmania donovani complex, while the isolate MHOM/CN/84/JS1 clustered with Leishmania tropica . The other 11 Chinese Leishmania isolates (MHOM/CN/90/WC, MCAN/CN/90/SC11, MHOM/CN/80/XJ801, MHOM/CN/85/GS4, MHOM/CN/84/SD1, MCAN/CN/86/SC7, MHOM/CN/54/#3, MHOM/CN/83/GS2, MHOM/CN/90/SC10H2, MHOM/CN/89/GS6 and MHOM/CN/ 89/GS5) form an unclassified group, defined as Leishmania sp., and the most relative species to this group is L. tarentolae . In the Bayesian analysis of the 7SL RNA gene, 9 Chinese Leishmania isolates also formed an unclassified group with L. tarentolae , including canine isolate 10, MHOM/CN/85/GS4, MHOM/CN/84/SD1, MCAN/CN/86/SC7, MHOM/CN/54/#3, MHOM/ CN/83/GS2, MHOM/CN/90/SC10H2, MHOM/CN/89/GS6 and MHOM/CN/89/GS5. We concluded that: (1) Chinese Leishmania isolates are non-monophyly group; (2) an unclassified group may exist in China, and the most relative species to this group is L. tarentolae ; (3) MHOM/CN/84/JS1, which was previously assigned as L. donovani , was most genetically related to L. tropica strain MHOM/SU/74/K27.

Several types of small RNAs have been proposed as gene expression repressors with great potential for use in gene therapy. RNA polymerase III (pol III) provides an ideal means of expressing small RNAs in cells because its normal products are small, highly structured RNAs that are found in a variety of subcellular compartments. We have designed cassettes that use human pol III promoters for the high-level expression of small RNAs in the cytoplasm, nucleoplasm, and nucleolus. The levels and subcellular destinations of the transcripts are compared for transcripts expressed using the U6 small nuclear RNA (snRNA), 5S ribosomal RNA (rRNA), and the 7SL RNA component of the signal recognition particle. The most effective location for a particular inhibitory RNA is not necessarily predictable; thus these cassettes allow testing of the same RNA insert in multiple subcellular locations. Several small interfering RNA (siRNA) inserts were tested for efficacy. An siRNA insert that reduces lamin expression when transcribed from the U6 snRNA promoter in the nucleus has no effect on lamin expression when transcribed from 5S rRNA and 7SL RNA-based cassettes and found in the nucleolus and cytoplasm. To test further the generality of U6-driven siRNA inhibitors, siRNAs targeting HIV were tested by co-transfection with provirus in cell culture. Although the degree of HIV-1 inhibition varied among inserts, results show that the U6 cassette provides a means of expressing an siRNA-like inhibitor of HIV gene expression.