Search

Abstract Background Enhancers are DNA sequences that serve as binding sites for regulatory proteins, and stimulate transcriptional activity independent of their positions and orientations with respect to the transcriptional initiation site. Previous studies considered that baculovirus homologous regions (hrs) function as enhancers in cis. In our study, a plasmid containing homologous region 3 (hr3) enhancer from Bombyx mori nucleopolyhedrovirus (BmNPV) failed to enhance transcription of promoter in other plasmid in co-transfection assays, but strong stimulation occurred when cells were infected by BmNPV. Results The cotransfection results of each BmNPV genomic library plasmid, hr3 plasmid and reporter plasmid showed that there were eight library plasmids stimulated the luciferase gene expression remarkably. Sequencing these plasmids revealed that each of them contained the ie-1 gene. Transfected plasmids, containing ie-1, hr3 and various origin promoter drove reporter gene showed the function was even retained. Cotransfection of hr3 functional dissected fragment and ie-1 revealed that the 30-bp imperfect palindrome destroyed fragment can't enhance reporter gene expression even though transfected with ie-1. Conclusion IE-1 was the only early factor of BmNPV that could act as a mediator for hr enhancer function in trans and the trans-function was achieved with a broad-spectrum of promoters. The 30-bp imperfect palindrome was the elementary molecular structure by which IE-1 participated in the enhancer function in trans.

Abstract Background achaete-scute complexe (AS-C) has been widely studied at genetic, developmental and evolutional levels. Genes of this family encode proteins containing a highly conserved bHLH domain, which take part in the regulation of the development of central nervous system and peripheral nervous system. Many AS-C homologs have been isolated from various vertebrates and invertebrates. Also, AS-C genes are duplicated during the evolution of Diptera. Functions besides neural development controlling have also been found in Drosophila AS-C genes. Results We cloned four achaete-scute homologs (ASH) from the lepidopteran model organism Bombyx mori, including three proneural genes and one neural precursor gene. Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif. These genes regulated promoter activity through the Class A E-boxes in vitro. Though both Bm-ASH and Drosophila AS-C have four members, they are not in one by one corresponding relationships. Results of RT-PCR and real-time PCR showed that Bm-ASH genes were expressed in different larval tissues, and had well-regulated expressional profiles during the development of embryo and wing/wing disc. Conclusion There are four achaete-scute homologs in Bombyx mori, the second insect having four AS-C genes so far, and these genes have multiple functions in silkworm life cycle. AS-C gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.

In recent years, the development of new vaccines such as nucleic acid vaccines, genetically engineered vaccines, and synthetic peptide vaccines has achieved rapid development. However, compared with traditional inactivated or live vaccines, these vaccines often have problems such as poor immunogenicity. Therefore, an adjuvant is needed to enhance its effect, and adjuvants have proven to be a key component in vaccines. There are many types of adjuvants, while currently no unified standard for the classification. At present, the most commonly used adjuvants are Aluminum adjuvant and Freund's adjuvant, but new generation vaccines will probably need new generation adjuvants. Thus, this review aims to showcase the current status of immune adjuvants, with the focus on immunomodulatory molecular adjuvant, antigen delivery adjuvant and compound adjuvant. This review provides new insights for the development of novel vaccine adjuvants.

The heat shock cognate 70-4 protein gene promoter (HSC70-4p) from Bombyx mori (BmHSC70-4p) is an ideal candidate for the transgenic silkworm due to its high transcriptional activity, and the homologous region 3 from Bombyx mori nucleopolyhedrovirus (BmNPVhr3) functions as an enhancer for several promoters. Using luciferase as a reporter gene and transient expression system in vivo and in vitro, we found that BmNPVhr3 can significantly increase the transcriptional activity of BmHSC70-4p and HSC70-4p from Bombyx mandarina (BmandHSC70-4p). Moreover, the transcriptional activity of the combination of BmHSC70-4p and BmNPVhr3 changed with developmental stages and hormone titers. These results suggest that the combination of BmHSC70-4 promoter and BmNPVhr3 enhancer is more effective candidate for the transgene or stable cell expression system in Bombyx mori.