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PubMed2004

Transcriptional control of B cell development and function.

The generation, development, maturation and selection of mammalian B lymphocytes is a complex process that is initiated in the embryo and proceeds throughout life to provide the organism an essential part of the immune system it requires to cope with pathogens. Transcriptional regulation of this highly complex series of events is a major control mechanism, although control is also exerted on all other layers, including splicing, translation and protein stability. This review summarizes our current understanding of transcriptional control of the well-studied murine B cell development, which bears strong similarity to its human counterpart. Animal and cell models with loss of function (gene "knock outs") or gain of function (often transgenes) have significantly contributed to our knowledge about the role of specific transcription factors during B lymphopoiesis. In particular, a large number of different transcriptional regulators have been linked to distinct stages of the life of B lymphocytes such as: differentiation in the bone marrow, migration to the peripheral organs and antigen-induced activation.

Animals↗

PubMed1992

Genetic cause of leukocyte adhesion molecule deficiency. Abnormal splicing and a missense mutation in a conserved region of CD18 impair cell surface expression of beta 2 integrins.

Patients with leukocyte adhesion molecule (CD11/CD18, beta 2 integrins) deficiency have structural defects in the common beta subunit (CD18), which prevent heterodimer formation and normal cell surface expression of these receptors, leading to life-threatening bacterial infections. To elucidate the nature of these defects in a patient with partial (type II) deficiency, abnormal CD18 cDNA clones were isolated, using the polymerase chain reaction to amplify the patient's B cell-derived cDNAs. Sequence analysis revealed two mutant alleles. cDNA clones, representing a maternal allele, contained both a 12-base pair insertion resulting in an in-frame addition of four amino acids between P247 and E248 and a C1756----T nucleotide transition, resulting in an R586----W substitution in the normal CD18 protein. The inframe insertion arose by a single nucleotide C----A transversion in the 3' terminus of an intron, generating aberrant splice acceptor site. Other cDNA clones contained an A1052----G nucleotide transition not present in either parent which resulted in an N351----S substitution. To determine the functional importance of these changes, cDNA encoding a normal alpha chain (CD11b) was cotransfected into COS with CD18 cDNAs encoding for wild-type, maternal mutant allele, or CD18 containing N351----S substitution. Immunostaining of transfectants with anti-CD18 monoclonal antibodies revealed no cell surface expression of the maternal mutant CD18, and 22% surface expression of N351----S CD18. Both the insertion and the N351----S mutations occurred in a 250 amino acid extracellular region of CD18 that is highly conserved among beta integrins supporting a role for this region in heterodimer formation.

Amino Acid Sequence↗

PubMed1999

Temperature sensitivity of two different steps in the viral life cycle of feline immunodeficiency virus.

Feline immunodeficiency virus (FIV) multiplication is totally blocked by incubation of infected cells at 41 degrees. This inhibition does not take place with a thermoresistant strain of FIV, designated m41, indicating the role played by the viral genome in temperature sensitivity. We have investigated the steps in the life cycle of wild-type FIV that are thermosensitive and found that they depend on the host cells infected. In CrFK cells, FIV replication was inhibited after the penetration step at 41 degrees. Synthesis of viral RNA and DNA was barely detectable and no viral antigen appeared in the extracellular medium. Nevertheless, viral multiplication resumed on incubation at 37 degrees, suggesting a state of latency at the elevated temperature. In peripheral blood mononuclear cells (PBMCs), the FIV cycle was inhibited at 41 degrees after the synthesis of viral DNA. Several viral mRNAs failed to appear as fully spliced products and no viral antigen was found in the extracellular medium. As in CrFK cells, viral multiplication occurred in PBMCs after a shift to the permissive temperature. These results suggest that at least two steps in the viral life cycle are sensitive to 41 degrees and that two different viral functions of the thermoresistant mutant m41 are modified to overcome temperature sensitivity.

Animals↗

PubMed2002

Human papillomavirus type 31 replication modes during the early phases of the viral life cycle depend on transcriptional and posttranscriptional regulation of E1 and E2 expression.

The E1 and E2 proteins are both required for papillomavirus DNA replication, and replication efficiency is controlled by the abundance of these factors. In human papillomaviruses (HPVs), the regulation of E1 and E2 expression and its effect on viral replication are not well understood. In particular, it is not known if E1 and E2 modulate their own expression and how posttranscriptional mechanisms may affect the levels of the replication proteins. Previous studies have implicated splicing within the E6 open reading frame (ORF) as being important for modulating replication of HPV type 31 (HPV31) through altered expression of E1 and E2. To analyze the function of the E6 intron in viral replication more specifically, we examined the effects of E6 splicing mutations in the context of entire viral genomes in transient assays. HPV31 genomes which had mutations in the splice donor site (E6SD) or the splice acceptor site (E6SA), a deletion of the intron (E6ID), or substituted heterologous intron sequences (E6IS) were constructed. Compared to wild-type (wt) HPV31, pHPV31-E6SD, -E6SA, and -E6IS replicated inefficiently while pHPV31-E6ID replicated at an intermediate level. Cotransfection of the E6 mutant genomes with an E1 expression vector strongly activated their replication levels, indicating that efficient expression of E1 requires E6 internal splicing. In contrast, replication was activated only moderately with an E2 expression vector. Replacing the wt E6 intron in HPV31 with a heterologous intron from simian virus 40 (E6SR2) resulted in replication levels similar to that of the wt in the absence of expression vectors, suggesting that mRNA splicing upstream of the E1 ORF is important for high-level replication. To examine the effects of E6 intron splicing on E1 and E2 expression directly, we constructed reporter DNAs in which the luciferase coding sequences were fused in frame to the E1 (E1Luc) or E2 (E2Luc) gene. Reporter activities were then analyzed in transient assays with cotransfected E1 or E2 expression vectors. Both reporters were moderately activated by E1 in a dose-dependent manner. In addition, E1Luc was activated by low doses of E2 but was repressed at high doses. In contrast, E2 had little effect on E2Luc activity. These data indicate that E1 expression and that of E2 are interdependent and regulated differentially. When the E6 splicing mutations were analyzed in both reporter backgrounds, only E1Luc activities correlated with splicing competence in the E6 ORF. These findings support the hypothesis that the E6 intron primarily regulates expression of E1. Finally, in long-term replication assays, none of the E6 mutant genomes could be stably maintained. However, cotransfection of the E6 splicing mutant genomes with pHPV31-E7NS, which contains a nonsense mutation in the E7 coding sequence, restored stable replication of some mutants. Our observations indicate that E1 expression and that of E2 are differentially regulated at multiple levels and that efficient expression of E1 is required for transient and stable viral replication. These regulatory mechanisms likely act to control HPV copy number during the various phases of the viral life cycle.

Carcinoma, Squamous Cell↗

PubMed2005

Occludin: structure, function and regulation.

Epithelial and/or endothelial barriers play a critical role in animal, including human, life forms. The tight junction (TJ) is an essential component of these barriers. Occludin is a major component of the TJ. The structure of occludin, including its gene splice variants and protein essential components have been elucidated. Phosphorylation/dephosphorylation plays a major role in regulation of occludin and TJ. Disruption of occludin regulation is an important aspect of a number of diseases. Strategies to prevent and/or reverse occludin downregulation may be an important therapeutic target.

Animals↗

PubMed1996

Sequences involved in the dimerisation of human T cell leukaemia virus type-1 RNA.

The formation of a genomic RNA dimer appears to be a critical step in the life cycle of all retroviruses. To investigate the site and nucleotide interactions involved in this process, a 531 bp DNA fragment encompassing sequences up- and downstream of the splice donor in human T cell leukaemia virus type 1 (HTLV-1) was inserted into a plasmid vector under the control of the SP6 promoter. RNA transcripts generated in vitro from this template formed dimers which could be dissociated by heating at 60-80 degrees C for 3 min. The physical properties of the dimeric RNA were not consistent with either Watson-Crick base pairing or guanine tetrad formation as being solely responsible for the interaction. Deletion mutagenesis identified a 32 nt sequence required for dimerisation. Computer modelling was carried out in order to identify putative RNA secondary structures within this essential region. A stem-loop structure was identified, the stem of which was conserved among different sequenced isolates of HTLV-1. This sequence also contains a 15 nt palindrome. We sought by disruptive and compensatory mutagenesis to define the possible roles of these two structures in dimer linkage.

Base Sequence↗

PubMed2005

A novel and efficient approach to discriminate between pre- and post-transcription HIV inhibitors.

Established anti-human immunodeficiency virus (HIV) treatments are not always effective or well tolerated, highlighting the need for further refinement of antiviral drug design and development. Given the multitude of molecular targets with which the anti-HIV agents can interact, studies on the mechanism of action of newly discovered HIV inhibitors are quite elaborate. In this article, we describe the use of an efficient reporter system allowing rapid discrimination between a pre- or post-transcriptional mode of action of anti-HIV compounds based on infection by a replication competent HIV-1 molecular clone expressing the green fluorescent protein as part of the nef multiply spliced RNA. Using fluorescence microscopy and flow cytometry, this system enabled us to differentiate between compounds acting at a pre- or post-transciptional level of the virus life cycle. Antiviral activities were determined for four reference compounds as well as one putative novel HIV inhibitor. The results obtained were in agreement with the known characteristics of the reference compounds and revealed that the novel compound interfered with a target before or overlapping with HIV transcription. We showed that during a single replication cycle, compounds inhibiting a molecular target occurring before or coinciding with HIV transcription suppressed GFP expression, whereas compounds interfering at a later stage (such as protease inhibitors, which act after transcription) did not inhibit GFP expression. This GFP-based reporter system is adaptable for high-throughput screening.

Anti-HIV Agents↗

PubMed2000

In a novel form of IFN-gamma receptor 1 deficiency, cell surface receptors fail to bind IFN-gamma.

Complete IFN-gamma receptor ligand-binding chain (IFNgammaR1) deficiency is a life-threatening autosomal recessive immune disorder. Affected children invariably die of mycobacterial infection, unless bone marrow transplantation is undertaken. Pathogenic IFNGR1 mutations identified to date include nonsense and splice mutations and frameshift deletions and insertions. All result in a premature stop codon upstream from the segment encoding the transmembrane domain, precluding cell surface expression of the receptors. We report herein two sporadic and two familial cases of a novel form of complete IFNgammaR1 deficiency in which normal numbers of receptors are detected at the cell surface. Two in-frame deletions and two missense IFNGR1 mutations were identified in the segment encoding the extracellular ligand-binding domain of the receptor. Eight independent IFNgammaR1-specific mAb's, including seven blocking antibodies, gave recognition patterns that differed between patients, suggesting that different epitopes were altered by the mutations. No specific binding of (125)I-IFN-gamma to cells was observed in any patient, however, and the cells failed to respond to IFN-gamma. The mutations therefore cause complete IFNgammaR1 deficiency by disrupting the IFN-gamma-binding site without affecting surface expression. The detection of surface IFNgammaR1 molecules by specific antibodies, including blocking antibodies, does not exclude a diagnosis of complete IFNgammaR1 deficiency.

Adolescent↗

PubMed1995

Recurrent mis-splicing of fibrillin exon 32 in two patients with neonatal Marfan syndrome.

The Marfan syndrome (MFS) is an autosomal dominant heritable disorder of connective tissue. Variable and pleiotropic clinical features are observed in the skeletal, ocular, and cardiovascular systems. The most severe end of the phenotypic spectrum of this disorder comprises a group of patients usually diagnosed at birth, who have a life expectancy of little more than a year. To distinguish this group of patients from those with classical MFS, we refer to them as neonatal Marfan syndrome (nMFS). These infants usually die of congestive heart failure rather than aortic aneurysmal disease, the most frequent cause of morbidity and mortality in classical MFS. Defects in fibrillin, an elastin-associated microfibrillar glycoprotein, are now known to cause both the classical and neonatal forms of MFS. Here we report the recurrent mis-splicing of fibrillin (FBN1) exon 32, a precursor EGF-like calcium binding domain, in two unrelated infants with nMFS. The mis-splicing, in one patient, was due to an A-->T transversion at the -2 position of the consensus acceptor splice site; while that in the second patient was caused by a G-->A transition at the +1 position of the donor splice site. Characterization of FBN1 mutations in individuals at the most severe end of the Marfan syndrome spectrum should provide greater understanding of the multiple domains and regions of fibrillin.

Alleles↗

PubMed2001

Display of complete life cycle of human papillomavirus type 16 in cultured placental trophoblasts.

Human papillomavirus (HPV) infection is threefold more prevalent in spontaneous abortion specimens compared to elective abortions preferentially targeting the placental trophoblasts in these specimens. Here by using infectious ceplar and Southern blot analysis, we demonstrate that the transfected HPV-16 genome de novo replicates in 3A trophoblasts in culture. Peak DNA replication occurred 9-24 days posttransfection, showing classic DNA forms I, II, and III and an 8-kb monomer band upon DpnI/BamHI digestion. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of mRNA expression revealed that E6 and E2 were significantly expressed by day 9, coinciding with HPV-16 DNA replication. However, significant L1 expression was delayed until day 18. L1 protein expression on day 18, but not day 9, was also confirmed by Western blot analysis. The production of HPV-16 virions was demonstrated by three techniques: the appearance of HPV-16 infectious units coinciding with L1 expression, the neutralization of these infectious units with known neutralizing anti-HPV-16 antibodies, and the appearance of spliced E1-E4 and E6-E7 transcripts (RT-PCR) in normal keratinocyte rafts infected with these trophoblast-produced HPV-16 infectious units. These data suggest that HPV-16 is carrying out its complete life cycle in trophoblasts. Previously, HPVs were known to productively replicate only in differentiating keratinocytes of skin. These findings expand HPV biology, support the hypothesis of a possible link between HPV and some spontaneous abortions, and present a new technology for studying HPV.

Cells, Cultured↗

PubMed1992

Nucleotide sequence and tissue distribution of three insulin-like growth factor I prohormones in salmon.

Tissue distribution and potential alternative splicing of insulin-like growth factor I (IGF-I) messenger RNA were studied using reverse transcriptase-polymerase chain reaction (RT-PCR) on RNA from several tissues at various stages of the life cycle of coho salmon (Oncorhynchus kisutch). DNA sequence analysis of RT-PCR products revealed three IGF-I mRNA transcripts, designated Ea-1, Ea-2, and Ea-3, which code for three distinct prohormones, IGF-IA-1, IGF-IA-2, and IGF-IA-3, respectively. The E-domain of proIGF-IA-1 is 35 amino acids long and shares 77% sequence identity with the E-domain of human proIGF-IA, which is also 35 amino acids long. The proIGF-IA-2 and proIGF-IA-3 E-domains are homologous to the proIGF-IA-1 E-domain but contain 27 and 39 amino acid inserts, respectively, between Lys86 and Glu87. In the human IGF-I gene Lys86 is coded by exon 4 and Glu87 is coded by exon 6. This suggests that Ea-2 and Ea-3 transcripts may be the result of alternative splicing during pre-mRNA processing. All three transcripts were readily detectable using a solution hybridization/RNase protection assay. Furthermore, RT-PCR and DNA sequencing analysis indicate the presence of three IGF-I prohormones in another member of the Salmonidae family, the Atlantic salmon (Salmo salar). An analysis of IGF-I and -II E-domains from several vertebrates suggests that certain chemical and physical properties of the molecule are well conserved despite wide variations in primary structure. Ea-1, Ea-2, and Ea-3 transcripts were found in whole embryos, and liver, muscle, and brain of juvenile and adult salmon. At least one IGF-I transcript was found in heart, kidney, testes, ovary, adipose tissue, and spleen of juvenile salmon. These results indicate that IGF-I is expressed during embryonic development of fish, and that most tissues are capable of IGF-I mRNA production. These data also indicate that pre-mRNA transcripts can be alternatively spliced to yield at least three prohormones.

Alternative Splicing↗

PubMed2004

Dilated cardiomyopathy caused by tissue-specific ablation of SC35 in the heart.

Many genetic diseases are caused by mutations in cis-acting splicing signals, but few are triggered by defective trans-acting splicing factors. Here we report that tissue-specific ablation of the splicing factor SC35 in the heart causes dilated cardiomyopathy (DCM). Although SC35 was deleted early in cardiogenesis by using the MLC-2v-Cre transgenic mouse, heart development appeared largely unaffected, with the DCM phenotype developing 3-5 weeks after birth and the mutant animals having a normal life span. This nonlethal phenotype allowed the identification of downregulated genes by microarray, one of which was the cardiac-specific ryanodine receptor 2. We showed that downregulation of this critical Ca2+ release channel preceded disease symptoms and that the mutant cardiomyocytes exhibited frequency-dependent excitation-contraction coupling defects. The implication of SC35 in heart disease agrees with a recently documented link of SC35 expression to heart failure and interference of splicing regulation during infection by myocarditis-causing viruses. These studies raise a new paradigm for the etiology of certain human heart diseases of genetic or environmental origin that may be triggered by dysfunction in RNA processing.

Animals↗

PubMed1993

Effects of 5-fluorouracil on mRNA.

Currently, there are a number of studies which suggest that FU can have pronounced effects on mRNA and its metabolism. However, the relevance of these changes to the antitumor effect of FU are still not clear. Generally, the mRNAs which have been studied to date involve those genes which are associated with the TS-directed effects of FU and have generally been limited to the changes in mRNA levels. The recent development of PCR methodology to investigate changes in pre-mRNA and splicing provides the tool to study a number of RNA effects of FU simultaneously. The major question is which mRNAs are important for study. DHFR mRNA has a half life of 11.5 in KB1BT cells (Will and Dolnick, 1989) and is thus, on a kinetic basis alone, unlikely to provide a significant RNA target for RNA-directed effects of FU. There is a greater likelihood that shorter lived mRNAs which not only turnover rapidly, but are important to cell proliferation will eventually be shown to be key targets for the effects of FU at the RNA level. Interestingly, many of the growth factors are encoded by short-lived and tightly regulated mRNAs (e.g. GM-CSF, Shaw and Kamen, 1986). In fact the half-lives of some of these mRNAs are regulated by U-rich sequences in their 3'-noncoding regions. The presence of U-rich sequences in these growth factor mRNAs and the small nuclear RNAs suggests these are worthwhile targets for studies, which could now be performed on clinical samples. Laboratory data which shows alterations in the small nuclear RNAs, under conditions which only provide for very low-level substitution of U residues by FU also suggest that RNA effects of FU may be a much more tightly related to cytotoxicity in vivo than previously thought.

Animals↗

PubMed2001

Molecular cloning and characterization of a gene encoding the 29-kDa proteasome subunit from Trypanosoma cruzi.

Antiserum raised against purified Trypanosoma cruzi proteasomes was used to isolate two cDNA clones, tcpr29 and tcpr29B, and the corresponding genomic sequence, termed tcpr29A. Both cDNAs and the gene contain a 798-bp ORF, coding for a 266-amino acid protein, with a predicted molecular mass of 29 kDa. Sequence comparisons show that the protein encoded by tcpr29 belongs to the alpha6 subfamily of proteasome subunits. Southern analysis indicated that tcpr29 subunit is encoded by a single-copy gene which maps to chromosome 20 of the CL Brener clone. Allelic variants were found in other T. cruzi isolates, suggesting heterozygosity for the gene in some and homozygosity in other strains. A spliced-leader addition site was identified 123 bp upstream from the start codon, generating a stable 1.5-kb transcript. Western analysis revealed that tcpr29A is constitutively expressed during the life cycle of the parasite.

5' Untranslated Regions↗

PubMed2001

A tale of two HSV-1 helicases: roles of phage and animal virus helicases in DNA replication and recombination.

Helicases play essential roles in many important biological processes such as DNA replication, repair, recombination, transcription, splicing, and translation. Many bacteriophages and plant and animal viruses encode one or more helicases, and these enzymes have been shown to play many roles in their respective viral life cycles. In this review we concentrate primarily on the roles of helicases in DNA replication and recombination with special emphasis on the bacteriophages T4, T7, and A as model systems. We explore comparisons between these model systems and the herpesviruses--primarily herpes simplex virus. Bacteriophage utilize various pathways of recombination-dependent DNA replication during the replication of their genomes. In fact the study of recombination in the phage systems has greatly enhanced our understanding of the importance of recombination in the replication strategies of bacteria, yeast, and higher eukaryotes. The ability to "restart" the replication process after a replication fork has stalled or has become disrupted for other reasons is a critical feature in the replication of all organisms studied. Phage helicases and other recombination proteins play critical roles in the "restart" process. Parallels between DNA replication and recombination in phage and in the herpesviruses is explored. We and others have proposed that recombination plays an important role in the life cycle of the herpesviruses, and in this review, we discuss models for herpes simplex virus type 1 (HSV-1) DNA replication. HSV-1 encodes two helicases. UL9 binds specifically to the origins of replication and is believed to initiate HSV DNA replication by unwinding at the origin; the heterotrimeric helicase-primase complex, encoded by UL5, UL8, and UL52 genes, is believed to unwind duplex viral DNA at replication forks. Structure-function analyses of UL9 and the helicase-primase are discussed with attention to the roles these proteins might play during HSV replication.

Animals↗

PubMed2006

Progressive vascular smooth muscle cell defects in a mouse model of Hutchinson-Gilford progeria syndrome.

Children with Hutchinson-Gilford progeria syndrome (HGPS) suffer from dramatic acceleration of some symptoms associated with normal aging, most notably cardiovascular disease that eventually leads to death from myocardial infarction and/or stroke usually in their second decade of life. For the vast majority of cases, a de novo point mutation in the lamin A (LMNA) gene is the cause of HGPS. This missense mutation creates a cryptic splice donor site that produces a mutant lamin A protein, termed "progerin," which carries a 50-aa deletion near its C terminus. We have created a mouse model for progeria by generating transgenics carrying a human bacterial artificial chromosome that harbors the common HGPS mutation. These mice develop progressive loss of vascular smooth muscle cells in the medial layer of large arteries, in a pattern very similar to that seen in children with HGPS. This mouse model should prove valuable for testing experimental therapies for this devastating disorder and for exploring cardiovascular disease in general.

Animals↗

PubMed1994

Identification of the primary site of the human immunodeficiency virus type 1 RNA dimerization in vitro.

The diploid genome of all retroviruses is made of two homologous copies of RNA intimately associated near their 5' end, in a region called the dimer linkage structure. Dimerization of genomic RNA is thought to be important for crucial functions of the retroviral life cycle (reverse transcription, translation, encapsidation). Previous in vitro studies mapped the dimer linkage structure of human immunodeficiency virus type 1 (HIV-1) in a region downstream of the splice donor site, containing conserved purine tracts that were postulated to mediate dimerization, through purine quartets. However, we recently showed that dimerization of HIV-1 RNA also involves sequences upstream of the splice donor site. Here, we used chemical modification interference to identify nucleotides that are required in unmodified form for dimerization of a RNA fragment containing nucleotides 1-707 of HIV-1 RNA. These nucleotides map exclusively in a restricted area upstream of the splice donor site and downstream of the primer binding site. They are centered around a palindromic sequence (GUGCAC279) located in a hairpin loop. Our results support a model in which dimer formation is initiated by the annealing of the palindromic sequences, possibly by a loop-loop interaction between the two monomers. Further experiments show that the deletion of the stem-loop or base substitutions in the loop abolish dimerization, despite the presence of the previously postulated dimer linkage structure. On the other hand, deletions of the purine tracts downstream of the splice donor site do not prevent dimerization. Therefore, we conclude that the palindromic region represents the dimerization initiation site of genomic RNA.

Base Sequence↗

PubMed2004

Autographa californica multiple nucleopolyhedrovirus exon0 (orf141), which encodes a RING finger protein, is required for efficient production of budded virus.

exon0 (orf141) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved baculovirus gene that codes for a predicted 261-amino-acid protein. Located in the C-terminal region of EXON0 are a predicted leucine-rich coiled-coil domain and a RING finger motif. The 5' 114 nucleotides of exon0 form part of ie0, which is a spliced gene expressed at very early times postinfection, but transcriptional analysis revealed that exon0 is transcribed as a late gene. To determine the role of exon0 in the baculovirus life cycle, we used AcMNPV bacmids and generated exon0 knockout viruses (Ac-exon0-KO) by recombination in Escherichia coli. Ac-exon0-KO progressed through the very late phases in Sf9 cells, as evidenced by the development of occlusion bodies in the nuclei of the transfected or infected cells. However, production of budded virus (BV) in Ac-exon0-KO-infected cells was reduced at least 3 orders of magnitude in comparison to that in wild-type virus infection. Microscopy revealed that Ac-exon0-KO was restricted primarily to the cells initially infected, exhibiting a single-cell infection phenotype. Slot blot assays and Western blot analysis indicated that exon0 deletion did not affect the onset or levels of viral DNA replication or the expression of IE1, IE0, and GP64 prior to BV release. These results demonstrate that exon0 is required for efficient production of BV in the AcMNPV life cycle but does not affect late occlusion-derived virus.

Amino Acid Motifs↗