Intranuclear topological distribution of HIV-1 trans-activators

Subcellular localization of human immunodeficiency virus type I (HIV-1) Tat and Rev was examined using a confocal laser scanning microscope (CLSM). In transfected COS-7 cells, Tat resided exclusively in the perinocleolar region, while Rev infiltrated fully into the nucleoli. The chimeric Tat in which the nucleolar targeting signal was replaced by that of Rev, which retains trans-acting activity of Tat, remained still in the perinucleolar region as wild-type Tat. Perinucleolar distribution of Tat protein suggests the existence of a novel nucleolar architecture that affects transcription.

[ATL and its virus]

A retrovirus called Human T cell leukemia virus type 1 (HTLV-1) is a causative agent of adult T cell leukemia (ATL). A cultured cell line called MT-2, produces constitutively HTLV-1. The characteristics of HTLV-1 produced from MT-2 has been extensively investigated. The molecular mechanism of ATL leukemogenesis by HTLV-1 is discussed.

[AIDS and its virus]

An etiological agent of AIDS is a human retrovirus called HIV. The genomic structure of HIV features regulatory genes in which tat and rev genes control the viral replication and affect cellular functions. Understanding their molecular mechanism may provide a clue to prevent the onset of AIDS from the viral carriers and to direct drug designing of AIDS.

[Basic understanding of retroviruses]

Retroviruses contain a reverse transcriptase in the virion that converts viral genomic RNA to proviral DNA. Retroviruses are divided into three groups; oncovirus, lentivirus, and spumavirus. The oncovirus group contains HTLV-1, which causes adult T-cell leukemia, encephalomyeloneuropathy, arthritis, and alveolo-bronchopathy. The lentivirus groups contains HIV, which causes acquired immunodeficiency syndrome and dementia. The genomic structures and functions of HTLV-1 and HIV have been demonstrated to explain the pathogenesis of these retroviruses.

Correlation of basic fibroblast growth factor expression levels with the degree of malignancy and vascularity in human gliomas

Basic fibroblast growth factor (FGF) is a mitogen, a differentiation factor for neuroectoderm-derived cells, and a potent angiogenic factor. The authors have previously demonstrated that the messenger ribonucleic acid of basic FGF is expressed in more than 90% of human gliomas. In the present study, they examined the expression of basic FGF in human glioma tissues using immunohistochemical techniques with a mouse monoclonal antibody against human basic FGF. They also correlated the basic FGF level with the histological grades of malignancy assessed by the number of nucleolar organizer regions (NOR's). Basic FGF was detected in 18 of 19 gliomas, whereas it was undetectable in two normal brains. The expression level of basic FGF peptide increased proportionally with the degree of malignancy. There was also a tendency for the number of NOR's in glioma cells to increase in glioma samples with a high level of basic FGF expression. Furthermore, most of the cases with increased vascularity demonstrated on cerebral angiograms showed a relatively high level of basic FGF expression of tumor cells and a large number of NOR's in endothelial cells in tumor tissues. These results suggest that basic FGF is actually produced in most gliomas and is involved in tumorigenesis and malignant progression as an autocrine growth factor. Moreover, basic FGF may play an important role in tumor neovascularization as a paracrine angiogenic factor.

Molecular diversity in amino-terminal domains of human calpastatin by exon skipping

Calpastatin, a specific inhibitor of calpain, consists of a unique N-terminal domain (domain L) and four repetitive calpain-inhibition domains (domains 1-4). Calpastatin cDNA of human was reported to have two deletions in domains L and 1, as compared with that of pig and rabbit. We isolated human calpastatin genomic DNA clones, and the sequence analysis revealed seven exons for domain L and five exons for domain 1. Those deletions in the human cDNA were retained in its genomic DNA as exons 3 and 11. By the reverse transcription polymerase chain reaction method, three calpastatin cDNAs, full-length domains L and 1, and two natural mutants with deletions in either exon 3 or in both exons 3 and 5, were cloned from human fibroblast WI-38 cell line mRNA. Domain L was found to be rich in basic amino acid residues, especially for exon 3, and its N-terminal half was highly conserved among species. The isoelectric points (pI) of domain L and domains 1-4 were calculated to be 10.27 and 4.26-4.90, respectively. Moreover, human tissues and cell lines displayed different patterns of reverse transcription polymerase chain reaction products in agarose gel electrophoresis. Therefore, alternative splicing is most likely the cause for the molecular diversity, and the multiple isoforms are implicated for specific physiological roles.

Induction of avascular yolk sac due to reduction of basic fibroblast growth factor by retinoic acid in mice

Vasculogenesis depends on autocrine secretion of basic fibroblast growth factor (bFGF) from capillary endothelial cells. Retinoic acid (RA) induced avascular yolk sac (AVY) of mouse embryos of dams given 60 mg/kg of RA orally on Day 8 of gestation and sacrificed 3 days later. We studied the localization and transcriptional expression of bFGF and FGF-receptor (flg), heparin-binding growth factor (HBGF) activity, localization of lysosomal enzymes and alpha 1-antitrypsin (AAT), and electron microscopy of the normal mouse visceral yolk sac (VYS) and AVY. bFGF, which is normally present in the endoderm of the VYS of 8-day-old embryos and in all components of the VYS by Day 11 of gestation, was reduced in the AVY. However, in the presence of bFGF in vitro capillary nets were restored in the AVY. The mRNA for bFGF was not detectable in either VYS or AVY, while flg mRNA was detected equally in both organs in Northern blotting. The characteristic distribution pattern of lysosomal enzymes, acid phosphatase, lysozyme, and cathepsin D, and AAT was altered in the AVY. The level of acid phosphatase and AAT was reduced to 10% in the AVY. Electron microscopy revealed a partial or total loss of lysosomal membranes where the contents of lysosomes fused with adjacent lysosomes and the external organelles. These results suggest that vitelline blood vessels are not developed by endogenous autocrine bFGF but by exogenous transcellular bFGF from absorptive endodermal cells. Retinoic acid does not affect the angiogenic capacity of the VYS mesenchyme but destroys lysosomes, which release hydrolytic enzymes, leading to degradation of AAT in the endodermal cells and then digestion of endocytosed bFGF.

Inhibition of human immunodeficiency virus type 1 Rev function by a Rev mutant which interferes with nuclear/nucleolar localization of Rev

A nonfunctional mutant of human immunodeficiency virus type 1 Rev was created by deleting seven amino acid residues within the nucleolar targeting signal. This mutant Rev remained in the cytoplasm in expressed cells and strongly inhibited the function of Rev by interfering with the nuclear/nucleolar localization of coexpressed Rev. These findings strongly suggest the multimerization of Rev in the cytoplasm before migration to the nucleus/nucleolus, where wild-type Rev functions as a trans-regulator.

[Evaluation of breath-hold multislice dynamic MRI of hepatocellular carcinomas]

The breath-hold multislice dynamic study (BMDS) in MRI, which can scan the entire liver during a single breath-holding, was applied to 16 patients with 30 focal lesions of hepatocellular carcinoma (HCC). The BMDS was performed at 20 seconds and 3 minutes after the bolus injection of Gd-DTPA, by gradient echo pulse sequence (FLASH). 29 nodules were detected in the BMDS, showing rapid enhancement on early phase and decline on delayed phase images. The BMDS was more sensitive than conventional MR images. Therefore, the BMDS seems to be useful for the diagnosis of HCC with multiple as well as solitary nodules.

Tax protein of human T-cell leukemia virus type I is required for maintenance of the transformed phenotype

We have isolated and characterized revertants of a clonal cell line (40MRatcl-1) of human T-cell leukemia virus type I Tax-transformed Rat1 cells. The 40MRatcl-1 cells contain a single copy of tax gene, form large colonies in soft agar, elicit tumors rapidly in nude mice and revert to the normal phenotype at low frequency. From one of its subclones (B7) bearing pSV2gpt DNA as a marker gene, four morphologically reverse-transformed cell lines were isolated. They display contact inhibition at confluency, lose the ability to form colonies in soft agar, fail to form tumors in nude mice and restore the transformed phenotype similar to that of 40MRatcl-1 cells by transfection with the tax-expression plasmid. Southern blot analysis revealed that they have lost the tax gene. Our results indicate that transformation of Rat1 cells by Tax is not the consequence of secondary mutations of cellular genes and that tax functions are directly required for establishment and maintenance of the transformed phenotype.

[Detection of intrahepatic lipids by 1H-MRS--studies by breath-holding & 1 cm3 VOI]

The authors performed 1H-MR spectroscopy (MRS) to depict lipids in the liver of 10 healthy volunteers. Spectra were obtained by a 1.5 T-MR unit, with STEAM from 1 x 1 x 1 cm3 VOI. Lipid peaks were depicted in 7 of the 10 volunteers by breath-holding 1H-MRS study, while in only 4 on normal breathing. The existence of lipids could not be depicted through chemical shift imaging adopting in-phase & opposed images. This suggests a clinical utility of 1H-MRS, particularly through breath-holding studies, in depicting lipids from 1 x 1 x 1 cm3 VOI in the liver in vivo.

Multiple forms of rat calpastatin cDNA in the coding region of functionally unknown amino-terminal domain

Partial mouse and rat calpastatin cDNAs containing functionally unknown amino-terminal regions were cloned by the polymerase chain reaction (PCR) method. Two types of clones were obtained for the rat calpastatin; one had a sequence similar to mouse and human calpastatins, while the other had a deletion of 38 amino acid residues in this region. Both types of the rat sequence differed from the previously reported rat calpastatin which had additional deletions. The occurrence of multiple forms of calpastatin suggests alternative splicing in the functionally unknown domain.

Expression of human T-cell leukemia virus type I protease in Escherichia coli

Human T-cell leukemia virus type I (HTLV-I) genome is believed to encode its own protease, although the protease has not yet been detected. To identify the HTLV-I protease, an in-frame gag (3' portion)-prt region was expressed in Escherichia coli. The 14-kDa product was detected using antisera against a synthetic peptide mimicking the fragment of HTLV-I protease, although the molecular weight of the primary translational product was 27,000. A cell extract had a proteolytic activity to cleave a synthetic peptide substrate containing the cleavage site of gag p19/p24 at the correct site in vitro. Replacement of the putative active site Asp-64 with Gly abolished both in vivo processing activity and in vitro proteolytic activity. These results suggest that the 14-kDa product is the mature enzymatically active HTLV-I protease generated through posttranslational autoprocessing in E. coli.

Structure of the active 27-residue fragment of human calpastatin

A synthetic 27-residue peptide corresponding to exon 1B of the endogenous inhibitor calpastatin contains a well-conserved region and has an ability to inhibit the cysteine endopeptidase calpain specifically. We examined the solution structure of this peptide in DMSO-d6 by two-dimensional 1H NMR spectroscopy. Although regular secondary structures such as alpha-helix and beta-sheet were not found, the region from Ile18 to Arg23 formed a well-defined structure with a type I beta-turn. This region coincided well with the highly conserved region of calpastatin. The result strongly suggests that this turn structure is essential for the inhibitory activity of calpastatin.

[Demonstration of the architecture of the tracheobronchial wall by MR imaging: an experimental study]

To study the potential of MRI to demonstrate the architecture of the tracheobronchial wall, resected tracheobronchi of rabbits were examined with MRI. As a result, epithelium and cartilage were demonstrated as relatively low intensity bands on T1- and T2-weighted images (T1WI and T2WI). The subepithelium was of intermediate-high intensity on T1WI and of markedly high intensity on T2WI and Gd-DTPA enhanced T1WI. Peritracheobronchial fat was of markedly high intensity on T1WI and of relatively low intensity on T2WI. In conclusion, MRI was found to have the potential to demonstrate the architecture of the tracheobronchial wall as 4 layers on each sequence.

Purification and characterization of human T-cell leukemia virus type I protease produced in Escherichia coli

Human T-cell leukemia virus type I (HTLV-I) protease has been purified to homogeneity from a strain of recombinant Escherichia coli. The protease was expressed as a larger precursor, which was autoprocessed to form a mature protease. Protein chemical analyses revealed the coding sequence of mature protease, which agreed with the putative sequence predicted from the sequence of bovine leukemia virus protease. The purified protease processed the natural substrate gag precursor (p53) to form gag p19 and gag p24. The protease activity was inhibited by pepstatin A. These results provide direct evidence that this protease belongs to the aspartic protease family and has an activity consistent with the protease in HTLV-I virion.

Induction of inflammatory arthropathy resembling rheumatoid arthritis in mice transgenic for HTLV-I

Human T cell leukemia virus type-I (HTLV-I) is the etiologic agent of adult T cell leukemia and has also been suggested to be involved in other diseases such as chronic arthritis or myelopathy. To elucidate pathological roles of the virus in disease, transgenic mice were produced that carry the HTLV-I genome. At 2 to 3 months of age, many of the mice developed chronic arthritis resembling rheumatoid arthritis. Synovial and periarticular inflammation with articular erosion caused by invasion of granulation tissues were marked. These observations suggest a possibility that HTLV-I is one of the etiologic agents of chronic arthritis in humans.

[Evaluation of muscle layer of the uterine body by dynamic MRI]

Gd-DTPA enhanced dynamic MR imaging was performed in 11 normal uteri using a 1.5-T MR unit in order to analyze normal dynamic patterns. After intravenous bolus administration of Gd-DTPA, dynamic study was performed with serial imaging-gradient echo (FLASH). In most cases of normal uteri, early enhancement was shown in peripheral zone that was similar to be junctional zone, forming inner region of muscle layer.

Inhibition of cell growth and tumorigenesis of human glioblastoma cells by a neutralizing antibody against human basic fibroblast growth factor

We report here that a neutralizing mouse monoclonal antibody against basic FGF inhibited both anchorage-dependent and anchorage-independent growth of U-87MG and T98G human glioblastoma cells and HeLa cells, all of which express both the basic FGF and the FGF receptor genes. In addition, the subcutaneous administration of this antibody significantly suppressed the tumor development of these tumor cells in nude mice. Therefore, basic FGF plays an important role in neoplastic growth of these cells. The neutralization of basic FGF will be effective in controlling the growth of tumors, such as glioblastoma and other cancer cells which bear basic FGF and FGF receptors.

Functional conversion from HIV-1 Rev to HTLV-1 Rex by mutation

A nucleolar localizing rev gene mutant M10 of human immunodeficiency virus type 1 (HIV-1) lost a Rev function completely, instead, gained a Rex activity of human T cell leukemia virus type 1 (HTLV-1). The obtained compatibility between Rev M10 and Rex with their own nucleolar targeting signal (NOS) suggests a common molecular mechanism of their post-transcriptional regulation, despite no sequence similarities of both proteins and their responsive RNA elements, respectively.

Direct measurement of calpastatin subtypes by sandwich enzyme immunoassay using monoclonal antibodies

Six stable hybridoma cell lines secreting monoclonal antibodies to human calpastatin were established. All monoclonal antibodies belong to the IgG1 subclass and recognized different epitopes on calpastatin. At least two groups were distinguished; the first group was specific for muscle-type (M-) calpastatin and the second group recognized not only M-calpastatin but also erythrocyte-type (E-) calpastatin. The inhibitory effect of all monoclonal antibodies on calpastatin activity was relatively low even at high concentrations of antibodies. Enzyme immunoassay systems were developed for direct determination of calpastatin subtypes in human cells requiring no other sample treatment than the disruption of the cells. The assay methods were, in principle, based on the sandwich enzyme immunoassay using epitope-specific monoclonal antibodies. The enzyme immunoassay system for M-calpastatin was specific for M-calpastatin and could not detect E-calpastatin. The enzyme immunoassay system for total calpastatin detected not only M-calpastatin but also E-calpastatin. The sensitivity of these assay systems was 10 pmol l-1 of calpastatins. Antigenicity of calpastatins was found to be unchanged in the presence of EDTA and haemoglobin. Good reproducibilities of within-and between-assay series and excellent recovery of exogenous calpastatins from cell lysates were observed. From these results, it seems that our newly developed subtype-specific enzyme immunoassay systems for calpastatins are useful in biochemical studies and clinical testing for determination of calpastatin subtypes.