Baculoviruses are a diverse group of large viruses with covalently close double-stranded DNA genomes of 80-200 kilobasepairs (kbp). Baculoviruses are pathogenic for invertebrates, primarily for insects. Baculovirus particles exist in two biochemically and morphologically distinct forms, an extracellular, nonoccluded (NOV), budded virus (BV) and an occluded form (OV), which are known as polyhedral derived viruses (PDV). Baculovirus genes expression is divided into three basic phases: early (E), late (L) and very late (VL). Briefly, these phases correspond biologically to: (E) reprogramming the cell for virus replication, (L) producing BV and (VL) producing OV. The several baculovirus genes are nonessential for virus replication, and their lack in viral genome does not have any effect on forming of infectious virus particles in the tissue culture. Some of the gene expression is driven by very strong late promoters (polyhedrin and p10) and their loci are ideal cloning sites for genes of heterologous proteins. The baculovirus expression vector system is the powerful tool for production of foreign proteins. One of the major advantages of the insect cell/baculovirus system over bacterial and mammalian systems is a very high expression of recombinant proteins, which is in many cases, antigenically, immunogenically and functionally similar to their native counterparts.
In this report we discuss the possibility of using antisense oligonucleotides specific to PAI-1 mRNA to reversibly decrease PAI-1 level in blood plasma and thus prolong a half-life time endogenous plasminogen activators in circulation.
A variety of recombinant DNA molecules have been introduced into the germ line of animals.The results transgenic animals have a diverse range of phenotypes, some of which were expected and some not anticipated.To data, the majority of transgenic animals are mice.However recombinant DNA has been introduced into agriculturally important animals such a sheep, rabbits, pigs, chickens, cattle and fish.In this report, we will survey the consequences of transgene expression in agriculturally important mammals in terms of their effects on growth.Also, we will review the data concerning the use of transgenic mammals as "bioreactors" for the production of recombinant proteins.
Baculovirus vectors are very useful in producing high levels of proteins. This system yields recombinant proteins similar to their original counterparts. Expression of foreign genes occurs in infected cells which provide a suitable environment for post-translational modifications and folding of the protein product. The size of baculovirus genome allows to insert large DNA segments (up to 25kb). Constructions of recombinant baculoviruses are very simple and need minimum of viral manipulation.
Over-expression of recombinant proteins in Escherichia coli, the most frequently used prokaryotic expression system, often results in the formation of intracellulary aggregated, insoluble folding intermediates. It is generally thought that protein aggregation is triggered by the failure of polypeptide intermediates to complete folding, leading to self-association. These aggregates are known as inclusion bodies or refractile bodies, since they appear upon microscopic observation as highly refractile areas. The formation of inclusion bodies often increases the yields of recombinant proteins and falicitates their isolation. The aggregated proteins are usually protected from proteases and do not harm host cells. Specific strategies are developed to produce bio-active proteins with the participation of inclusion bodies. These procedures include: 1) isolation and purification of inclusion bodies, 2) solubilization of the protein aggregates, and 3) renaturation of solubilized proteins involving formation of native disulphide bonds.
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