The pUC plasmids, an M13mp7-derived system for insertion mutagenesis and sequencing with synthetic universal primers

A series of plasmid vectors containing the multiple cloning site (MCS7) of M13mp7 has been constructed. In one of these vectors a kanamycin-resistance marker has been inserted into the center of the symmetrical MCS7 to yield a restriction-site-mobilizing element (RSM). The drug-resistance marker can be cleaved out of this vector with any of the restriction enzymes that recognize a site of the flanking sequences of the RSM to generate an RSM with either various sticky ends or blunt ends. These fragments can be used for insertion mutagenesis of any target molecule with compatible restriction sites. Insertion mutants are selected by their resistance to kanamycin. When the drug-resistance marker is removed with PstI, a small in-frame insertion can be generated. In addition, two new MCSs having single restriction sites have been formed by altering the symmetrical structure of MCS7. The resulting plasmids pUC8 and pUC9 allow one to clone doubly digested restriction fragments separately with both orientations in respect to the lac promoter. The terminal sequences of any DNA cloned in these plasmids can be characterized using the universal M13 primers.

A new pair of M13 vectors for selecting either DNA strand of double-digest restriction fragments

The strategy of shotgun cloning with M13 is based on obtaining random fragments used for the rapid accumulation of sequence data. A strategy, however, is sometimes needed for obtaining subcloned sequences preferentially out of a mixture of fragments. Shotgun sequencing experiments have shown that not all DNA fragments are obtained with the same frequency and that the redundant information increases during the last third of a sequencing project. In addition, experiments have shown that particular fragments are obtained more frequently in one orientation, allowing the use of only one of the two DNA strands as a template for M13 shotgun sequencing. Two new M13 vectors, M13mp8 and M13mp9, have been constructed that permit the cloning of the same restriction fragment in both possible orientations. Consequently, each of the two strands becomes a (+) strand in a pair of vectors. The fragments to be cloned are cleaved with two restriction enzymes to produce a fragment with two different ends. The insertion of such a fragment into the vector can occur only in one orientation. Since M13mp8 and M13mp9 have their array of cloning sites in an antiparallel order, either orientation for inserting a double-digest fragment can be selected by the choice of the vector.

New pUC-derived cloning vectors with different selectable markers and DNA replication origins

Four new Escherichia coli cloning vectors are described, pUC6S, pUC21, pUK21 and pOK12. These vectors contain a polylinker or multiple cloning site (MCS) with the recognition sequences for 28 restriction enzymes. Plasmids pUC21, pUK21, and pOK12 contain the MCS in the N-terminal end of the lacZ alpha fragment allowing blue/white screening for inserts. To potentially increase the stability of some inserts that may encode toxic proteins, the strength of the lacZ promoter present on these vectors has been reduced. Plasmids pUC6S and pUC21 carry the bla gene encoding ampicillin resistance, while pUK21 and pOK12 contain the gene encoding kanamycin resistance. Plasmid pOK12 carries the replicon from P15A, resulting in a lower copy number pUC-type vector. Plasmid pUC6S carries the ori and bla gene present on all pUC vectors, but does not contain any lac sequences. Plasmids pUC21 and pUK21 contain the M13 intergenic region allowing for the production of plasmid single-stranded DNA. To improve the yield of ss plasmid DNA, two plasmid cis-acting factors that affect yield were also examined: the effect of plasmid-derived transcription across the M13 ori, and the effect of delecting the M13 minus-strand ori from the plasmid.

The human cytomegalovirus chemokine receptor US28 mediates vascular smooth muscle cell migration

Human cytomegalovirus (HCMV) infection of smooth muscle cells (SMCs) in vivo has been linked to a viral etiology of vascular disease. In this report, we demonstrate that HCMV infection of primary arterial SMCs results in significant cellular migration. Ablation of the chemokine receptor, US28, abrogates SMC migration, which is rescued only by expression of the viral homolog and not a cellular G protein-coupled receptor (GPCR). Expression of US28 in the presence of CC chemokines including RANTES or MCP-1 was sufficient to promote SMC migration by both chemokinesis and chemotaxis, which was inhibited by protein tyrosine kinase inhibitors. US28-mediated SMC migration provides a molecular basis for the correlative evidence that links HCMV to the acceleration of vascular disease.

Frequent detection of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) DNA in saliva of human immunodeficiency virus-infected men: clinical and immunologic correlates

The prevalence, quantity, temporal pattern, and clinical and immunologic correlates of shedding of Kaposi's sarcoma (KS)-associated herpesvirus (KSHV; or human herpesvirus [HHV]-8) DNA in saliva were studied. KSHV DNA was detected in saliva from 18 (75%) of 24 human immunodeficiency virus (HIV)-positive patients with KS and from 1 of 1 HIV-negative patient with KS, 3 (15%) of 20 HIV-positive patients without KS, and none of 24 controls. KSHV DNA levels ranged from 10(2.4) to 10(6) copies/mL and were lower than levels for Epstein-Barr virus but comparable to those for HHV-6. Detection of KSHV DNA in saliva was not associated with oral KS or decreased peripheral blood CD4 cell counts. KSHV DNA was not detected in semen. Resistance of KSHV DNA from saliva to DNase treatment was consistent with the presence of virions. These data suggest that KSHV can replicate in the oropharynx and that salivary contact could contribute to KSHV transmission.

Activation of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) lytic replication by human cytomegalovirus

The majority of Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells identified in vivo contain latent KSHV, with lytic replication in only a few percent of cells, as is the case for the cells of Kaposi's sarcoma (KS) lesions. Factors that influence KSHV latent or lytic replication are not well defined. Because persons with KS are often immunosuppressed and susceptible to many infectious agents, including human cytomegalovirus (HCMV), we have investigated the potential for HCMV to influence the replication of KSHV. Important to this work was the construction of a recombinant KSHV, rKSHV.152, expressing the green fluorescent protein (GFP) and neo (conferring resistance to G418). The expression of GFP was a marker of KSHV infection in cells of both epithelial and endothelial origin. The rKSHV.152 virus was used to establish cells, including human fibroblasts (HF), containing only latent KSHV, as demonstrated by latency-associated nuclear antigen expression and Gardella gel analysis. HCMV infection of KSHV latently infected HF activated KSHV lytic replication with the production of infectious KSHV. Dual-color immunofluorescence detected both the KSHV lytic open reading frame 59 protein and the HCMV glycoprotein B in coinfected cells, and UV-inactivated HCMV did not activate the production of infectious KSHV-GFP. In addition, HCMV coinfection increased the production of KSHV from endothelial cells and activated lytic cycle gene expression in keratinocytes. These data demonstrate that HCMV can activate KSHV lytic replication and suggest that HCMV could influence KSHV pathogenesis.

Acquired immune deficiency in Haitians: opportunistic infections in previously healthy Haitian immigrants

We describe acquired immune deficiency manifested by opportunistic infections in 10 previously healthy heterosexual Haitian men. The opportunistic pathogens included Toxoplasma gondii (in four patients), Cryptococcus neoformans (in one), Pneumocystis carinii (in four patients), and Candida albicans (in three). Six of the patients also had Mycobacterium tuberculosis. Immunologic studies of three patients showed a decrease in the numbers and activity of helper T cells, with normal or increased populations of suppressor T cells. Serologic markers for previous infections from hepatitis A, cytomegalovirus, and herpes simplex virus were detected in several patients. Six of the patients died despite specific antimicrobial therapy. The clinical and immunologic findings in these 10 Haitians are similar to those reported in drug addicts and homosexuals with the acquired immune-deficiency syndrome.

Transmissible Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) in saliva of men with a history of Kaposi's sarcoma

We have evaluated the physical state and infectious nature of Kaposi's sarcoma-associated herpesvirus (KSHV) in the saliva of nine persons with past or current Kaposi's sarcoma (KS). KSHV DNA in saliva had the physical characteristics of DNA present in virions. Inoculation of 293 cells with cell-free saliva fluid resulted in the persistence of KSHV DNA in culture for at least 13 passages of the cells. The addition of tetradecanoyl phorbol acetate to KSHV-infected 293 cells led to increased viral DNA. Two virus-specific RNAs were detected by reverse transcriptase PCR in 293 cells infected with cell-free saliva fluid and in cells present in saliva from subjects with KSHV salivary shedding. These results indicate that infectious KSHV can be present in saliva of patients with KS.

Association of ERBB2 gene status with histopathological parameters and disease-specific survival in gastric carcinoma patients

The clinical significance of ERBB2 amplification/overexpression in gastric cancer remains unclear. In this study, we evaluated the ERBB2 status in 463 gastric carcinomas using immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH), and compared the findings with histopathological characteristics and with disease-specific survival. ERBB2 overexpression (2+ and 3+) and amplification (ratio ERBB2/CEP17⩾2) were found in 43 (9.3%) and 38 (8.2%) gastric carcinomas, respectively. Perfect IHC/FISH correlation was found for the 19 cases scored as 0 (all negative by FISH), and also for the 25 cases scored as 3+ (all positive by FISH). One out of six carcinomas scored as 1+ and 12 out of 18 carcinomas scored as 2+ were positive by FISH. ERBB2 amplification was associated with gastric carcinomas of intestinal type (P=0.007) and with an expansive growth pattern (P=0.021). ERBB2 amplification was detected in both histological components of two mixed carcinomas, indicating a common clonal origin. A statistically significant association was found between ERBB2 amplification and worse survival in patients with expansive gastric carcinomas (P=0.011). We conclude that ERBB2 status may have clinical significance in subsets of gastric cancer patients, and that further studies are warranted to evaluate whether patients whose gastric carcinomas present ERBB2 amplification/overexpression may benefit from therapy targeting this surface receptor.

Human herpesvirus 8 interaction with target cells involves heparan sulfate

Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma associated herpesvirus (KSHV) is associated with Kaposi's sarcoma and primary effusion lymphoma. In vivo, HHV-8 DNA and transcripts have been detected in B cells, endothelial cells, macrophages, and epithelial cells. HHV-8 infects a variety of cell lines of human and animal origin, leading to latent or abortive infection. This study shows that the broad cellular tropism of HHV-8 may be in part due to its interaction with the ubiquitous host cell surface molecule, heparan sulfate (HS). This conclusion is based on the following findings: (i) HHV-8 infection of human foreskin fibroblast (HFF) cells was inhibited in a dose-dependent manner by soluble heparin, a glycosaminoglycan closely related to HS. Chondroitin sulfates A and C did not inhibit HHV-8 infection. (ii) Enzymatic removal of HFF cell surface HS with heparinase I and III reduced HHV-8 infection. (iii) Soluble heparin inhibited the binding of radiolabeled HHV-8 to human B cell lines, embryonic kidney epithelial (293) cells, and HFF cells, suggesting interference at the virus attachment stage. (iv) Cell surface adsorbed HHV-8 was displaced by soluble heparin. (v) Radiolabeled HHV-8 also bound to wild-type HS expressing Chinese hamster ovary (CHO-K1) cells. In contrast, binding of virus to mutant CHO cells deficient in HS was significantly reduced. These data show that the gamma2 herpesvirus HHV-8, similar to some members of alpha, beta, and gamma2 herpesviruses, adsorbs to cells by binding to cell surface HS-like moieties. Heparin did not completely prevent the binding and infectivity of HHV-8, suggesting that HHV-8 interactions with HS could be the first set of ligand-receptor interaction leading to the binding with one or more host cell receptors essential for the subsequent viral entry process.

A pilot study of a system for grading of drainage blebs after glaucoma surgery

PURPOSE

To develop and evaluate a novel bleb grading scheme for clinical and photographic evaluation.

METHOD

A system for grading bleb photographs using widely applicable parameters was designed, and reference color photographs printed. A prospective masked agreement study was undertaken comparing slit lamp examination with mono and stereo photographs; 36 eyes of 28 patients with previous glaucoma surgery were graded according to defined parameters on a 1 to 10 scale clinically at the slit lamp by four ophthalmologists and two optometrists. Standardized stereo and mono photographs of the blebs were taken on the same day. The photographs were graded at least one week later in a masked fashion by the same observers, with grading of mono and stereo photographs also separated by one week. Analysis was performed to determine the variability and agreement between slit lamp results and photographic results, and to identify the presence of systematic bias.

RESULTS

High levels of agreement were found between slit lamp and both stereo and mono photographs for vascularity indices, bleb wall thickness, and bleb elevation. Lower levels of agreement were found for the relative components of demarcated versus diffuse areas of the bleb, and for the total width of the bleb. The interquartile range for the median difference between slit lamp and photograph grading was -1.0 to 1.0 for all criteria except diffuse component (-2.0 to 2.0), and the median difference for all scores was 0.0. The median interobserver difference for all criteria was 0.0; the quartile range for all scores was between -0.5 and 1.0 except for diffuse component and width assessments whose quartiles fell in the -1.75 to 1.0 range. Examiners agreed with photographic grading within +/- 1 in more than 80% of gradings for vascularity and bleb height, within +/- 1 in more than 75% of gradings for bleb wall thickness, within +/- 2 in 61% of bleb width assessments, and +/- 2 in 59% of diffuse component.

CONCLUSION

This bleb grading system is reproducible clinically and photographically. High levels of agreement between scores for photographs versus slit lamp examination were found for most categories, with good interobserver agreement for both photograph and slit lamp grading. Further refinement of scoring and reference photographs is required for optimization, especially for grading of bleb morphology.

Inferring parameters of mutation, selection and demography from patterns of synonymous site evolution in Drosophila

Selection acting on codon usage can cause patterns of synonymous evolution to deviate considerably from those expected under neutrality. To investigate the quantitative relationship between parameters of mutation, selection, and demography, and patterns of synonymous site divergence, we have developed a novel combination of population genetic models and likelihood methods of phylogenetic sequence analysis. Comparing 50 orthologous gene pairs from Drosophila melanogaster and D. virilis and 27 from D. melanogaster and D. simulans, we show considerable variation between amino acids and genes in the strength of selection acting on codon usage and find evidence for both long-term and short-term changes in the strength of selection between species. Remarkably, D. melanogaster shows no evidence of current selection on codon usage, while its sister species D. simulans experiences only half the selection pressure for codon usage of their common ancestor. We also find evidence for considerable base asymmetries in the rate of mutation, such that the average synonymous mutation rate is 20-30% higher than in noncoding regions. A Bayesian approach is adopted to investigate how accounting for selection on codon usage influences estimates of the parameters of mutation.

Functional analysis of the human cytomegalovirus US28 gene by insertion mutagenesis with the green fluorescent protein gene

The protein encoded by the US28 gene of human cytomegalovirus (HCMV) has homology to G protein-coupled receptors (GCR). Previous studies demonstrated that recombinant US28 protein can bind the beta class of chemokines (K. Neote, D. DiGregorio, J. Y. Mak, R. Horuk, and T. J. Schall, Cell 72:415-425, 1993) and induce a rise in intracellular calcium after the binding of chemokines (J. L. Gao and P. M. Murphy, J. Biol. Chem. 269:28539-28542, 1994). In order to investigate the function of the US28 protein in virus-infected cells, a recombinant HCMV (HV5.8) was constructed, with the US28 open reading frame disrupted by the insertion of the Escherichia coli gpt gene and the gene for the green fluorescent protein. The US28 gene is not required for growth in human fibroblasts (HF). HF infected with wild-type HCMV bound RANTES at 24 h postinfection and demonstrated an intracellular calcium flux induced by RANTES. In cells infected with HV5.8, RANTES did not bind or induce a calcium flux, demonstrating that US28 is responsible for the beta-chemokine binding and induced calcium signaling in HCMV-infected cells. The ability of the US28 gene to bind chemokines was shown to cause a significant reduction in the concentration of RANTES in the medium of infected cells. Northern analysis of RNA from infected cells showed that US28 is an early gene, while US27 (another GCR) is a late gene.

Gene amplification of the histone methyltransferase SETDB1 contributes to human lung tumorigenesis

Disruption of the histone modification patterns is one of the most common features of human tumors. However, few genetic alterations in the histone modifier genes have been described in tumorigenesis. Herein we show that the histone methyltransferase SETDB1 undergoes gene amplification in non-small and small lung cancer cell lines and primary tumors. The existence of additional copies of the SETDB1 gene in these transformed cells is associated with higher levels of the corresponding mRNA and protein. From a functional standpoint, the depletion of SETDB1 expression in amplified cells reduces cancer growth in cell culture and nude mice models, whereas its overexpression increases the tumor invasiveness. The increased gene dosage of SETDB1 is also associated with enhanced sensitivity to the growth inhibitory effect mediated by the SETDB1-interfering drug mithramycin. Overall, the findings identify SETDB1 as a bona fide oncogene undergoing gene amplification-associated activation in lung cancer and suggest its potential for new therapeutic strategies.

The pFF plasmids: cassettes utilising CaMV sequences for expression of foreign genes in plants

A plant expression cassette was constructed using the cauliflower mosaic virus 35S 5' regulatory region with the enhancer duplicated and the 35S polyadenylation signal. Insertion of a polylinker between the transcription initiation and polyadenylation sites allows for easy cloning of genes. To test the usefulness of the cassette chimeric bacterial genes were prepared. The constructs were introduced into Nicotiana tabacum suspension culture cells by the particle bombardment process. Expression of the beta-glucuronidase reporter gene was verified by histochemical staining. Stable kanamycin and hygromycin resistant transgenic lines were obtained after introduction of chimeric genes encoding the enzymes neomycin phosphotransferase and hygromycin B phosphotransferase, respectively. The number of stable transformants was approximately 2% of the cells that transiently expressed the beta-glucuronidase reporter gene.

Evidence of latency and reactivation of both herpes simplex virus (HSV)-1 and HSV-2 in the genital region

While superinfection with different herpes simplex virus (HSV) types has been demonstrated in animals, the ability of the two HSV types to colonize and reactivate in the same anatomic region in humans has not been well demonstrated. In 6 patients, both HSV-1 and HSV-2 was recovered from genital lesions. In 4 of them, who initially acquired genital HSV-1 infection, subsequent HSV-2 infection presented as a prolonged episode of genital lesions and a marked increase in the frequency of genital recurrences. While most of the subsequent clinical reactivations were HSV-2, in 2 patients the recurrence rate of genital HSV-1 increased after the acquisition of HSV-2. These data demonstrate the ability of a second HSV type to infect the same anatomic region and illustrate the difference in reactivation frequency of the two types in the same person. Typing of HSV isolates may be useful in persons with recent alteration in recurrence rates of genital HSV.

Stereotypies in Rett syndrome: Analysis of 83 patients with and without detected MECP2 mutations

BACKGROUND

Hand stereotypies are considered a hallmark of Rett syndrome (RTT) and are usually described as symmetric movements at the midline. However, related pathologies may show the same type of involuntary movement. Furthermore, patients with RTT also have stereotypies with other localizations that are less well characterized.

METHODS

We analyzed stereotypies in 83 patients with RTT, 53 with and 30 without a mutation detected in the MECP2 gene. Patients were observed and videotaped always by the same pediatric neurologist. Stereotypies were classified, and data were submitted to statistical analysis for comparison of mutation-positive and -negative patients and analysis of their evolution with the disease.

RESULTS

All the patients showed hand stereotypies that coincided with or preceded the loss of purposeful hand movements in 62% of the patients with MECP2 mutations. The hair pulling stereotypy was more frequent in the group with detected mutations, whereas hand washing was not. Hand gaze was absent in all RTT patients with MECP2 mutations. Patients with MECP2 mutations also had more varied stereotypies, and the number of stereotypies displayed by each patient decreased significantly with age in this group. In all patients, stereotypies other than manual tended to disappear with the evolution of the disease.

CONCLUSIONS

Although symmetric midline hand stereotypies were not specific to patients with an MECP2 mutation, some of the other stereotypies seemed to be more characteristic of this group. In patients younger than 10 years and meeting the necessary diagnostic criteria of Rett syndrome, the association of hand stereotypies without hand gaze, bruxism, and two or more of the other stereotypies seemed to be highly indicative of the presence of an MECP2 mutation.

Beam loading in the nonlinear regime of plasma-based acceleration

A theory that describes how to load negative charge into a nonlinear, three-dimensional plasma wakefield is presented. In this regime, a laser or an electron beam blows out the plasma electrons and creates a nearly spherical ion channel, which is modified by the presence of the beam load. Analytical solutions for the fields and the shape of the ion channel are derived. It is shown that very high beam-loading efficiency can be achieved, while the energy spread of the bunch is conserved. The theoretical results are verified with the particle-in-cell code OSIRIS.

Selectable insertion and deletion mutagenesis of the human cytomegalovirus genome using the Escherichia coli guanosine phosphoribosyl transferase (gpt) gene

We describe the mutagenesis of the IRSI-US5 region of the human cytomegalovirus genome, demonstrating the potential of the E. coli guanosine phosphoribosyl transferase (gpt) gene as a selectable marker for insertion and deletion mutagenesis of high passage (AD169, Towne) as well as low passage (Toledo) strains of virus. Despite evidence suggesting that the US3 gene product may play a regulatory role, disruption of this gene with a gpt insert had no effect on growth of any of these strains of virus in resting or dividing human fibroblasts, or in human thymus plus liver implants in SCID-hu mice. Transcripts of the gpt gene, under control of the herpes simplex virus thymidine kinase promoter adjacent to the US3 enhancer in the viral genome, accumulated with delayed early (beta) kinetics. Mutants with deletions in the IRS1 and US3-US5 regions were isolated by back-selection against gpt with the drug 6-thioguanine by growing virus in human Lesch-Nyhan (hypoxanthine-guanine phosphoribosyl transferase deficient) skin fibroblasts immortalized with human papillomavirus oncogenes. Thus, we demonstrate a dependable method for insertion and deletion mutagenesis that can be applied to any region of the viral genome.

Stable multi-GeV electron accelerator driven by waveform-controlled PW laser pulses

The achievable energy and the stability of accelerated electron beams have been the most critical issues in laser wakefield acceleration. As laser propagation, plasma wave formation and electron acceleration are highly nonlinear processes, the laser wakefield acceleration (LWFA) is extremely sensitive to initial experimental conditions. We propose a simple and elegant waveform control method for the LWFA process to enhance the performance of a laser electron accelerator by applying a fully optical and programmable technique to control the chirp of PW laser pulses. We found sensitive dependence of energy and stability of electron beams on the spectral phase of laser pulses and obtained stable 2-GeV electron beams from a 1-cm gas cell of helium. The waveform control technique for LWFA would prompt practical applications of centimeter-scale GeV-electron accelerators to a compact radiation sources in the x-ray and γ-ray regions.

Genes in the HindIII J fragment of the murine cytomegalovirus genome are dispensable for growth in cultured cells: insertion mutagenesis with a lacZ/gpt cassette

The organization and function of the genes encoded within the HindIII J region of the murine cytomegalovirus genome were analyzed by transcript mapping and cDNA isolation, nucleotide sequence analysis and identification of open reading frames (ORFs), and construction of recombinant viruses carrying insertions disrupting five of the seven ORFs. This region was found to encode five beta transcripts and one gamma transcript in addition to two beta transcripts previously mapped to the sgg1 locus. Seven open reading frames were identified, and one was recognized as a homolog of a human cytomegalovirus US22 gene family. The five largest ORFs contained within the HindIII J fragment (sgg1, HJ4, HJ5, HJ6, and HJ7) were each disrupted by the insertion of a lacZ/gpt genetic marker cassette. The growth kinetics of all recombinant viruses were investigated and found to be the same as wild-type parental virus, indicating that these five ORFs were dispensable for growth in cell culture.

Structure and function of the murine cytomegalovirus sgg1 gene: a determinant of viral growth in salivary gland acinar cells

The salivary gland has long been recognized as an important target organ for cytomegalovirus replication in the infected host. A viral gene, denoted sgg1, plays an important role for replication in the salivary gland even though it is dispensable for growth in other organs or in cultured cells. The nucleotide sequence of this gene and of cDNA clones representing two spliced transcripts (1.5 and 1.8 kb in size) has been determined. The more abundant 1.5-kb transcript contains a 312-amino-acid (aa) open reading frame (ORF) and encodes the corresponding 37-kDa protein (Sgg1) when expressed in transfected COS-7 cells. The 1.8-kb transcript initiates upstream of the 1.5-kb transcript and contains a 108-aa ORF in addition to the 312-aa ORF. This longer cDNA also encodes the 37-kDa protein Sgg1, although at lower abundance than the 1.5-kb cDNA. Sgg1 localizes to the cytoplasm of COS-7 cells, which is consistent with the predicted structural characteristics of the 312-aa ORF: a type 1 integral membrane protein. During viral infection, expression of both sgg1 transcripts is highest at early times (8 to 12 h) after infection; only the 1.5-kb transcript is present, at low levels, late in infection. A recombinant virus, RM868, carrying a lacZ-gpt insertion within sgg1, fails to express Sgg1 protein and exhibits reduced growth in the salivary gland. RM868 retains the capacity to disseminate in the infected mouse and to enter serous acinar cells, although it fails to replicate efficiently in this cell type. These results suggest that sgg1 is critical for high levels of viral replication in the salivary gland.

Nucleotide sequence analysis of a zein genomic clone with a short open reading frame

The nucleotide sequence of the zein genomic clone (W22)Z7 and its flanking sequences from the W22 inbred line of maize is reported. The sequence is 1587 bp long and contains 444 bp of 5' noncoding sequence and 342 bp of 3' noncoding sequence. The Z7 sequence belongs to a large complex multigene family and is a member of the B49 subfamily. It is 86% homologous to other known sequences from the same subfamily, but contains four in-frame termination codons caused by single base changes. Its flanking regions contain the usual eukaryotic transcriptional signals.

Human cytomegalovirus infection of caco-2 cells occurs at the basolateral membrane and is differentiation state dependent

Epithelial cells are known to be a major target for human cytomegalovirus (HCMV) infection; however, the analysis of virus-cell interactions has been difficult to approach due to the lack of in vitro models. In this study, we established a polarized epithelial cell model using a colon epithelial cell-derived cell line (Caco-2) that is susceptible to HCMV infection at early stages of cellular differentiation. Infection of polarized cells was restricted to the basolateral surface whereas virus was released apically, which was consistent with the apical and not basolateral surface localization of two essential viral glycoproteins, gB and gH. HCMV infection resulted in the development of a cytopathology characteristic of HCMV infection of colon epithelium in vivo, and infection did not spread from cell to cell. The inability of HCMV to infect Caco-2 cells at late stages of differentiation was due to a restriction at the level of viral entry and was consistent with the sequestration of a cellular receptor for HCMV. These observations provide the first evidence that restriction of HCMV replication in epithelial cells is due to a receptor-mediated phenomenon.