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M Sauter

Publications and source records attributed to M Sauter.

At least 37 records · Page 2Linked to original sources
PubMed1999

Expression of two PIP genes in rapidly growing internodes of rice is not primarily controlled by meristem activity or cell expansion.

Membrane intrinsic proteins facilitate movement of small molecules often times functioning as water channels. We have identified two genes from rice which encode proteins with characteristic features of plasma membrane intrinsic proteins (PIP). They possess six membrane-spanning domains, an NPA repeat, overall high sequence homologies and characteristic C- and N-terminal hallmark motifs which allowed assignment of OsPIP1a to the PIP1 subfamily and of OsPIP2a to the PIP2 subfamily. OsPIP1a and OsPIP2a showed similar but not identical expression patterns. The two genes were expressed at higher levels in seedlings than in adult plants and expression in the primary root was regulated by light. In internodes of deepwater rice plants which were induced to grow rapidly by submergence, transcript levels were slightly induced in the intercalary meristem (IM) and slightly reduced in the elongation zone (EZ) after 18 h. In internodes of GA-induced excised stem sections transcript levels transiently declined in the IM and EZ after 1 h and subsequently recovered to elevated levels after 18 h. GA also induced OsPIP expression in non-growing tissue after 18 h. In the IM of submergence-induced stem sections transcript levels remained constitutive. The different growth-promoting treatments showed no direct correlation between growth rate and OsPIP gene expression in dividing or expanding cells. In fact, treatment of excised stem sections with ABA or drought stress induced similar changes in OsPIP expression in the growing zone during the first 6 h as GA did. We conclude that regulation of OsPIP1a and OsPIP2a expression is not primarily controlled by growth. GA-induced growth may however change the water status of cells which in turn results in altered PIP abundance.

Abscisic Acid↗
PubMed1999

High prevalence of hepatitis G virus (HGV) infections in dialysis staff.

BACKGROUND: Patients on renal replacement therapy, haemodialysis (HD), or after kidney transplantation (TX), are known to be at risk of acquiring blood-borne infections (HBV, HCV). GBV-C/Hepatitis G virus (HGV) has been described recently and is considered to cause blood-borne infections. The aim of this study was to analyse the risk for the medical staff of HD and TX patients to acquire HGV infection. METHODS: Eighty-five HD patients and 86 TX recipients were compared with 49 health-care workers and 64 blood donors as controls. The HGV prevalence was determined by RT-PCR and antibodies to E2 protein. RESULTS: A high prevalence of HGV was found in the medical staff (24%) which nearly corresponded to the prevalence of the patients (TX 36%, HD 25%) but not to the controls (9%). In contrast, the prevalence of HCV was low in the medical staff (2%) and controls (0%) but high in HD (13%) and TX (13%). Age and duration of employment in the department did not significantly influence the HGV prevalence in staff. The number of viraemic subjects in staff was high, possibly indicating a more recent infection. CONCLUSION: An occupational risk for HGV exists in medical staff of dialysis and transplant patients. Further routes of transmission than only parenteral may play a role in this setting.

Aged↗
PubMed1999

Adventitious root growth and cell-cycle induction in deepwater rice

Deepwater rice (Oryza sativa) is adapted to survive conditions of severe flooding over extended periods of time. During such periods adventitious roots develop to provide water, nutrients, and anchorage. In the present study the growth of adventitious roots was induced by treatment with ethylene but not auxin, cytokinin, or gibberellin. Root elongation was enhanced between 8 and 10 h after submergence. The population of cells in the S phase and expression of the S-phase-specific histone H3 gene increased within 4 to 6 h. Within 6 to 8 h the G2-phase population increased. Cell-cycle activation was accompanied by sequential induction of a cdc2-activating kinase homolog, R2, of two cdc2 genes, cdc2Os-1 and cdc2Os-2, and of three cyclin genes, cycA1;3, cycB2;1, and cycB2;2, but only induction of the R2 gene expression preceded the induction of the S phase, possibly contributing to cell-cycle regulation in the G1 phase. Both cdc2 genes were expressed at slightly higher levels during DNA replication. Transcripts of the A-type cyclin accumulated during the S and G2 phases, and transcripts of the B-type cyclins accumulated during the G2 phase. Cyclin expression was induced at all nodes with a similar time course, suggesting that ethylene acts systemically and that root primordia respond to ethylene at an early developmental stage.

Journal Article↗
PubMed1999

Expression of a gibberellin-induced leucine-rich repeat receptor-like protein kinase in deepwater rice and its interaction with kinase-associated protein phosphatase.

We identified in deepwater rice (Oryza sativa L.) a gene encoding a leucine-rich repeat receptor-like transmembrane protein kinase, OsTMK (O. sativa transmembrane kinase). The transcript levels of OsTMK increased in the rice internode in response to gibberellin. Expression of OsTMK was especially high in regions undergoing cell division and elongation. The kinase domain of OsTMK was enzymatically active, autophosphorylating on serine and threonine residues. A cDNA encoding a rice ortholog of a kinase-associated type 2C protein phosphatase (OsKAPP) was cloned. KAPPs are putative downstream components in kinase-mediated signal transduction pathways. The kinase interaction domain of OsKAPP was phosphorylated in vitro by the kinase domain of OsTMK. RNA gel-blot analysis indicated that the expression of OsTMK and OsKAPP was similar in different tissues of the rice plant. In protein-binding assays, OsKAPP interacted with a receptor-like protein kinase, RLK5 of Arabidopsis, but not with the protein kinase domains of the rice and maize receptor-like protein kinases Xa21 and ZmPK1, respectively.

Amino Acid Sequence↗
PubMed1998

Functional characterization of the protease of human endogenous retrovirus, K10: can it complement HIV-1 protease?

To investigate the biochemical properties of the protease encoded by the human endogenous retrovirus, K10 (HERV-K), 213 amino acids of the 3'-end of the HERV-K protease (PR) open reading frame were expressed in Escherichia coli. Autocatalytic cleavage of the expressed polypeptide resulted in an 18.2 kDa protein which was shown to be proteolytically active against a fluorogenic peptide used as a substrate for HIV-1 protease. On the basis of sequence homology and molecular modeling, the 106 N-terminal amino acids of HERV-K PR were predicted to comprise a retroviral protease core domain. An 11.6 kDa protein corresponding to this region was expressed and shown to be a fully functional enzyme. The 11.6 kDa domain of HERV-K PR is unusually stable over a wide pH range, exhibits optimal catalytic activity between pH 4.0 and 5.0, and exists as a dimer at pH 7.0 with a Kd of 50 microM. Like HIV-1 PR, the HERV-K PR core domain is activated by high salt concentrations and processes HIV-1 matrix-capsid polyprotein at the authentic HIV-1 PR recognition site. However, both the 18.2 and 11.6 kDa forms of HERV-K PR were highly resistant to a number of clinically useful HIV-1 PR inhibitors, including ritonavir, indinavir, and saquinavir. This raises the possibility that HERV-K PR may complement HIV-1 PR during infection, and could have implications for protease inhibitor therapy and drug resistance.

Amino Acid Sequence↗
PubMed1998

Human endogenous retrovirus (HERV)-K transcripts in germ cell and trophoblastic tumours.

Prompted by the observation of retroviral particle formation in teratocarcinoma cell lines and the consistent finding of antibodies against Gag and Env proteins encoded by human endogenous retrovirus (HERV)-K genomes in the sera of patients with classical seminoma, we studied ovarian and testicular germ cell tumours, their precursor lesions, dysgenetic gonads, and trophoblast lesions for expression of HERV-K sequences by in situ hybridization using radioactive and non-radioactive probes. HERV-K transcripts were detected in all testicular and ovarian germ cell tumours with the exception of teratomas and spermatocytic seminomas. HERV-K expression was also common to testicular carcinoma in situ as well as gonocytes of dysgenetic gonads. Among gestational trophoblastic lesions, HERV-K expression was regularly found in choriocarcinomas, but not in molar lesions. The patterns of HERV-K expression suggest a common molecular pathogenesis of most germ cell tumour entities and malignant gestational trophoblastic disease. They furthermore support the concept of carcinoma in situ as a precursor lesion common to most testicular germ cell neoplasms. The detection of HERV-K gene products in body fluids and tissues may aid diagnosis and monitoring of germ cell tumours and related lesions.

Female↗
PubMed1998

Detection of human papillomavirus 16 transcriptional activity in cervical intraepithelial neoplasia grade III lesions and cervical carcinomas by nested reverse transcription-polymerase chain reaction and in situ hybridization.

Continued expression of the oncogenes E6 and E7 of human papilloma virus "high risk" type 16 (HPV16) initiates neoplastic transformation and maintenance of the malignant phenotype in cervical carcinoma cells. The transcriptional activity of the HPV16 E6/E7 oncogenes was investigated in HPV16-containing cervical cell lines, cervical carcinomas, and cervical intraepithelial neoplasia grade III lesions using the techniques of reverse transcription-polymerase chain reaction (RT-PCR), Southern blotting, and in situ hybridization. To facilitate detection of the full-length HPV16 E6/E7 oncogene transcript and its characteristic splice products E6*I and E6*II in cervical tissues, a nested RT-PCR (nRT-PCR) assay was designed. Specific detection of HPV E6/E7 oncogene transcripts in clinical specimens was found to be improved by nRT-PCR, being as sensitive as the combination of conventional RT-PCR and subsequent Southern blot hybridization. Regarding the progression of premalignant lesions to cervical cancer, detection of the HPV transcriptional activity by nRT-PCR may provide additional information for risk evaluations. Moreover, improvements in the amplification of HPV oncogene transcripts may also be advantageous for monitoring the activity of HPV before and after transcript-targeted gene therapy of cervical cancer.

Carcinoma↗
PubMed1997

Differential expression of a CAK (cdc2-activating kinase)-like protein kinase, cyclins and cdc2 genes from rice during the cell cycle and in response to gibberellin.

Progress through the eukaryotic cell cycle is regulated by cyclin-dependent cdc2 protein kinases. In rice (Oryza sativa L), two cdc2 protein kinases, cdc2Os-1 and cdc2Os-2, and two cyclins, cycOs1 and cycOs2, have been described. In this study, we report on the cell-cycle phase-specific expression of these genes. Using partially synchronized suspension cells from rice, we found that cdc2Os-1 was expressed constitutively throughout the cell cycle. The cdc2Os-2 transcript level was elevated in G1 and S phase. The cycOs1 and cycOs2 transcripts increased steadily through G2 and dropped off rapidly in mitosis as is typical for mitotic cyclins. We hypothesize that the cdc2Os-2 gene product acts in G1/S and that the growth-promoting hormone gibberellin (GA) that induces expression of cdc2Os-2, cycOs1 and cycOs2 in the intercalary meristem of deepwater rice internodes accelerates G1/S phase progression through increased expression of cdc2Os-2 and G2/M phase progression through increased expression of the mitotic cyclins cycOs1 and cycOs2. The R2 gene from rice has 55% sequence identity to the cdc2-activating kinase (CAK) family of protein kinases which have been shown to phosphorylate and thereby activate cdc2 protein kinases in animals and yeast. In partially synchronized suspension cells, R2 mRNA levels were elevated in G1 and S phase. In GA-treated rice internodes, R2 transcript levels were elevated in the meristem and part of the elongation zone. These results are consistent with a role for R2 in regulating G1/S phase progression.

Amino Acid Sequence↗
PubMed1997

[Gene products of human endogenous retrovirus (HERV)-K in germ cell and trophoblastic tumors].

Antibodies against Gag and Env proteins encoded by human endogenous retrovirus (HERV)-K genomes are found in the sera of patients with classical seminoma. This prompted us to study ovarian and testicular germ cell tumors, their precursor lesions, dysgenetic gonads, and trophoblast lesions for expression of HERV-K sequences by in situ hybridization using radioactive and non-radioactive probes. Expression of HERV-K sequences was found in all testicular and ovarian germ cell tumors with the exception of teratomas and spermatocytic seminomas. HERV-K expression was also found in testicular intraepithelial neoplasia (so-called carcinoma in situ) as well as in gonocytes of dysgenetic gonads. Among gestational trophoblastic lesions, HERV-K expression was regularly found in choriocarcinomas, but not in non-invasive molar lesions. There was no evidence for HERV-K expression in differentiated embryonal and adult tissues. The findings point to a common molecular pathogenesis of most germ cell tumor entities and malignant gestational trophoblastic disease. They furthermore support the concept of carcinoma in situ as a precursor lesion common to most testicular germ cell tumors. Conceivably, the detection of HERV-K gene products in body fluids and tissues will aid diagnosis and monitoring of germ cell tumors and related lesions.

Adult↗
PubMed1996

Specificity of antibodies directed against Env protein of human endogenous retroviruses in patients with germ cell tumors.

We report here that 85% of the patients with germ cell tumors (GCTs) produce antibodies directed against Env protein of human endogenous retroviruses. Individuals that received antitumor treatment showed a decrease with time in their antibody titers. Importantly, of the rare cases of non-GCT individuals with Env-antibodies (n= 15, 0.8%), none produced antibodies directed against the transmembrane domain (TM), whereas all tested Env-positive GCT patients (n= 49) generated such antibodies at high titers. TM is required for Env to be expressed at the cell surface. Thus, anti-TM antibodies constitute highly specific markers for GCT and may hint at a function of Env during tumorigenesis.

Animals↗
PubMed1996

Plant cyclins: a unified nomenclature for plant A-, B- and D-type cyclins based on sequence organization.

The comparative analysis of a large number of plant cyclins of the A/B family has recently revealed that plants possess two distinct B-type groups and three distinct A-type groups of cyclins. Despite earlier uncertainties, this large-scale comparative analysis has allowed an unequivocal definition of plant cyclins into either A or B classes. We present here the most important results obtained in this study, and extend them to the case of plant D-type cyclins, in which three groups are identified. For each of the plant cyclin groups, consensus sequences have been established and a new, rational, plant-wide naming system is proposed in accordance with the guidelines of the Commission on Plant Gene Nomenclature. This nomenclature is based on the animal system indicating cyclin classes by an upper-case roman letter, and distinct groups within these classes by an arabic numeral suffix. The naming of plant cyclin classes is chosen to indicate homology to their closest animal class. The revised nomenclature of all described plant cyclins is presented, with their classification into groups CycA1, CycA2, CycA3, CycB1, CycB2, CycD1, CycD2 and CycD3.

Amino Acid Sequence↗
PubMed1996

Regulation of human endogenous retrovirus-K Gag expression in teratocarcinoma cell lines and human tumours.

Human endogenous retrovirus-K (HERV-K) Gag protein is produced by both Tera 1 and PA-1 (ovarian teratocarcinoma) cells, but only Tera 1 cells release the protein in the form of particles. It was unclear how Gag production was regulated in these cell types. Although both Tera 1 and PA-1 cells express Gag, demethylation upon treatment with 5-azacytidine (5-AZC) or exposure to the chromatin-modifying agent n-butyrate resulted in an increase in Gag protein levels only in Tera 1 cells. Consistent with this cell type-specific overexpression of Gag in response to demethylation, exposure to 5-AZC caused undermethylation of the gag gene and adjacent 5'LTR only in Tera 1 but not PA-1 or Raji cells. Similarly and importantly, undermethylation of gag sequences and expression of Gag were also correlated in primary human testicular tumours. These results therefore suggest that endogenous retroviral elements are subject to regulation through the methylation of CpG dinucleotides.

Azacitidine↗
PubMed1996

Characterization of the human endogenous retrovirus K proteinase.

The proteinase of the human endogenous retrovirus K (HERV-K) shows similarity to retrovirus aspartic proteinases. It is translated from a transcript composed of gag and prt. The proteinase was expressed either as full-length native protein or as truncated protein in Escherichia coli. Functional protein was demonstrated by its autocatalytic cleavage into an 18 kDa fragment recognized by a polyclonal antiserum. This autocatalytic cleavage was specifically inhibited by a human immunodeficiency virus type 1 proteinase inhibitor. The HERV-K proteinase expressed in E. coli was capable of cleaving HERV-K Gag translated in vitro. Major protein fragments of 39 and 30 kDa, and minor protein fragments of 26, 22 and 21 kDa were obtained. Similar fragments are also observed in the human teratocarcinoma cell line Tera1. Our data suggest that the HERV-K proteinase is functionally equivalent to other retrovirus proteinases and thus probably functions in the processing of Gag precursor protein.

Endopeptidase K↗
PubMed1996

Pathogenesis of murine enterovirus myocarditis: virus dissemination and immune cell targets.

In order to identify organ and cellular targets of persistent enterovirus infection in vivo, immunocompetent mice (SWR/J, H-2q) were inoculated intraperitoneally with coxsackievirus B3 (CVB3). By use of in situ hybridization for the detection of enteroviral RNA, we show that CVB3 is capable of inducing a multiorgan disease. During acute infection, viral RNA was visualized at high levels in the heart muscle, pancreas, spleen, and lymph nodes and at comparably low levels in the central nervous system, thymus, lung, and liver. At later stages of the disease, the presence of enteroviral RNA was found to be restricted to the myocardium, spleen, and lymph nodes. To characterize infected lymphoid cells during the course of the disease, enteroviral RNA and cell-specific surface antigens were visualized simultaneously in situ in spleen tissue sections. In acute infection, the majority of infected spleen cells, which are located primarily at the periphery of lymph follicles, were found to express the CD45R/B220+ phenotype of pre-B and B cells. Whereas viral RNA was also detected in certain CD4+ helper T cells and Mac-1+ macrophages, no enteroviral genomes were identified in CD8+ cytotoxic/suppressor T cells. Later in disease, the localization of enteroviral RNA revealed a persistent type of infection of B cells within the germinal centers of secondary follicles. In addition, detection of the replicative viral minus-strand RNA intermediate provided evidence for virus replication in lymphoid cells of the spleen during the course of the disease. These data indicate that immune cells are important targets of CVB3 infection, providing a noncardiac reservoir for viral RNA during acute and persistent myocardial enterovirus infection.

Acute Disease↗
PubMed1996

Human endogenous retroviral element k10 (HERV-K10): chromosomal localization by somatic hybrid mapping and fluorescence in situ hybridization.

The human endogenous retrovirus K10 (HERV-K10) was mapped to human chromosomes using HERV-K10 specific PCR primers on a somatic hybrid mapping panel. A non-random chromosomal location was demonstrated with PCR signals on chromosomes 1, 3, 4, 5, 6, 7, 10, 11, 12, 14, 15, 19, 20, 21, 22 and Y. There was a lack of PCR products on the other chromosomes, even after hybridization with a HERV-K10 specific probe. To further localize the HERV-K10 sequence we used fluorescence in situ hybridization. Chromosomes 1, 3, 6, 7, 10, 11, 12 and 22 were found to contain several HERV-K10 sequences in different regions. The presence of several integration sites on some chromosomes is consistent with previous studies demonstrating 30-50 copies of the HERV-K10 sequence per haploid genome. The mapping information reported in this study will assist the analysis of the biological significance of the HERV-K10 sequence.

Base Sequence↗
PubMed1996

Expression of human endogenous retrovirus K elements in germ cell and trophoblastic tumors.

Antibodies against proteins encoded by human endogenous retrovirus (HERV)-K family genes are consistently found in the sera of patients with classical seminoma. Furthermore, HERV-K Gag-encoded protein could be detected in corresponding tumor biopsies. Addressing questions as to the extent of HERV gene expression in biologically related lesions, we studied various testicular and ovarian germ cell tumors (GCTs), GCT precursor lesions, and gestational trophoblastic disease (GTD) for the presence of HERV-K gene transcripts in tissue sections. By in situ hybridization using four non-overlapping, isotopically labeled RNA probes specific for HERV-K gag and env sequences on archival tissue samples, consistent HERV-K expression of gag and env genes was found to be common to all GCTs and their testicular precursor lesions with the exception of teratomas, mature and immature, and spermatocytic seminomas. HERV-K expression was also found in malignant GTD (choriocarcinoma) but not in benign GTD (noninvasive molar pregnancy). There was no evidence for HERV-K expression in differentiated embryonal and adult tissues as well as a total of 53 tumors other than GCT or GTD. The findings point to a common molecular pathoetiology of GCT and malignant GTD, have implications for the classification of GCTs, and support the concept of carcinoma in situ as a precursor lesion common to all forms of testicular GCT.

Adult↗
PubMed1995

Coxsackieviral proteins functionally recognize the polioviral cloverleaf structure of the 5'-NTR of a chimeric enterovirus RNA: influence of species-specific host cell factors on virus growth.

The 5'-non-translated region (NTR) of enteroviruses contains secondary structures which do not only serve in the initiation of translation but also in the initiation of plus-strand RNA synthesis by binding of viral and cellular proteins. To investigate a very early step of enteroviral replication by cis- and trans-complementation, 220 nucleotides of the 5'-region of coxsackievirus B3 (CVB3) were exchanged with the corresponding region of poliovirus type 1 (PV1) to yield the chimeric virus CVB3[PV5']. The viability of this chimera demonstrates that the polioviral cloverleaf structure of the 5'-NTR is functional in the replication of a chimeric CVB3 RNA. The HeLa-generated chimera reveals a 4-nucleotide deletion (nt 232-235) within a short direct repeat. Besides clearly reduced growth characteristics in all permissive cell lines, the chimera exhibits a small-plaque phenotype. The host range is changed since the virus grows well in human HeLa cells, but does not replicate in murine YAC-1 and Ltk cells, although these cell lines are permissive for the replication of both parental viruses. Moreover, in simian Vero, COS-1, or FRhK-4 cells the HeLa-generated chimera CVB3[PV5'] exhibits a strict temperature sensitivity at 39 degrees C. After infection of simian cells with high m.o.i. in situ hybridization data reveal that the chimera replicates in single cells at almost normal rates indicating that only a small fraction of HeLa-generated virus is able to multiplicate in simian cell lines. After passaging the virus chimera in Vero cells two further mutations occur at nucleotide positions 185 and 227. Since this genome region is known to interact with viral proteins and several host cell factors during the initiation of replication and translation, interactions of such factors with either viral RNA or viral proteins may be disturbed but still functional at permissive temperatures in HeLa cells and simian cell lines, whereas murine cell lines are not permissive. These experiments suggest that phenomena like host range, tissue tropism and cell-type specificity may be explained as a complex interplay of cellular surface receptors and intracellular host factors. Such intracellular factors could be part of the enteroviral initiation complex during the plus-strand RNA synthesis or during translation initiation and could be expressed in a tissue-, organ- or species-specific way or might be regulated developmentally.

Animals↗