Identification of inhibitor-of-differentiation 2 (Id2) as a modulator of neuronal apoptosis

Inhibitor-of-differentiation 2 (Id2) belongs to a family of transcriptional modulators that are characterized by a helix loop helix region but lack the basic amino acid domain. During development, Id2 antagonizes differentiation mediated by the retinoblastoma protein, probably by scavenging downstream E-box basic helix-loop-helix proteins. Here, using differential display RT-PCR, we identify Id2 as an induced gene during serum and potassium deprivation-induced apoptosis of cerebellar granule neurons. Consistent with a biological role for induced Id2 messenger RNA and protein expression in neuronal cell death, expression of Id2 antisense RNA, or targeted deletion of the Id2 gene in neurons from Id2 knock-out mice, protect from apoptosis. Further, gene transfer- mediated overexpression of Id2 induces neuronal cell death both in high potassium and low potassium conditions. Thus, the present study defines a role for Id2 in the modulation of neuronal apoptosis.

Two targets in pCF10 DNA for PrgX binding: their role in production of Qa and prgX mRNA and in regulation of pheromone-inducible conjugation

PrgX is the primary cytoplasmic protein involved in negative control of pheromone-inducible conjugation functions of the Enterococcus faecalis plasmid pCF10. PrgX is believed to act in concert with an antisense RNA called Qa to inhibit readthrough of transcription from the prgQ promoter into the pCF10 genes mediating conjugation functions; PrgX also positively regulates its own expression, as well as that of Qa. We found two DNA target sites for PrgX binding in the intergenic region between the prgX and prgQ genes of pCF10. The primary binding site near prgX includes an 11 bp palindromic sequence and showed relatively high affinity for His-tagged PrgX (His-PrgX). The secondary binding site is between the -35 and -10 regions of the prgQ promoter, and contains only a half of the palindromic sequence; this binding site showed weaker affinity. A region of pCF10 including the prgQ promoter and the secondary binding site reduced Qa RNA levels greatly and this reduction was overcome by the presence of the primary binding site and PrgX. In constructs where the binding sites were mutated individually or in combination, the intracellular levels of PrgX protein and Qa RNA were reduced significantly. On the basis of these results, we propose that both DNA binding sites are required for the autoregulation of PrgX expression and for positive regulation of Qa RNA.

Imprinting of the murine MAS protooncogene is restricted to its antisense RNA

The Mas protooncogene encodes a G protein-coupled receptor with the common seven transmembrane domains and may be involved in the actions of angiotensins. The gene is located in close proximity to the paternally imprinted Igf2r gene and its maternal imprinting has been reported but remained controversial. We used mice carrying a targeted deletion of the Mas protooncogene on the maternal or paternal chromosome to clarify this issue. In all Mas-expressing organs of adult mice such as heart, kidney, testis or brain, no Mas mRNA was missing in heterozygous animals inheriting the deleted allele from the father excluding mono-allelic paternal expression. However, we show exclusive paternal expression of a Mas antisense RNA, confirming the maternal imprinting of this antisense RNA in all investigated adult tissues and in embryos. Our results strongly suggest that Mas is not imprinted in mice but that an antisense RNA probably starting in the neighboring Igf2r gene is maternally imprinted in both embryos and adult organs.

Characterization of the small antisense CI RNA that regulates bacteriophage P4 immunity

In the immune state bacteriophage P4 prevents expression of the replication functions by premature termination of transcription. A small RNA, the CI RNA, is the trans acting factor that regulates P4 immunity, by pairing to complementary target sequences and causing premature transcription termination. The CI RNA is matured by RNAse P and PNPase from the leader region of the same operon it regulates. In this work we better characterize this molecule. CI RNA copy number was determined to be around 500 molecules per lysogenic cell. By S(1) mapping we defined the 3'-end at 8423(+/-1); thus CI RNA is 79(+/-1) nt long. The minimum region for correct processing requires two bases upstream of the CI RNA 5'-end and the CCA sequence at the 3'-end. Computer analysis by FOLD RNA of CI RNA sequence predicts a cloverleaf-like structure formed by a double-stranded stalk, a minor and a major stem loop, and a single-stranded bulge. We analysed several cI mutations, which fall either in the single or double-stranded CI RNA regions. Base substitutions in the main loop and in the single-stranded bulge apparently did not change CI RNA structure, but affected its activity by altering the complementarity with the target sequences, whereas a mutation in the secondary stem had a disruptive effect on CI RNA secondary structure. The effects of this latter mutation were suppressed by a base substitution that restored the complementarity with the corresponding base in the stem. Base substitutions in the main stem caused only local alterations in the secondary structure of CI. However, when the substitutions concerned either G8501 or its complementary base at the bottom of the stem, CI RNA was not correctly processed.

Stress, the immune system and vulnerability to degenerative disorders of the central nervous system in transgenic mice expressing glucocorticoid receptor antisense RNA

Current research evidence suggests that interactions between genetic and environmental factors contribute to modulate the susceptibility to degenerative disorders, including inflammatory and autoimmune diseases of the central nervous system (CNS). In this context, bidirectional communication between the neuroendocrine and immune systems during ontogeny plays a pivotal role in programming the development of neuroendocrine and immune responses in adult life, thereby influencing the predisposition to several disease entities. Glucocorticoids (GCs), the end products of the hypothalamic-pituitary-adrenocortical (HPA) axis, gender and signals generated by hypothalamic-pituitary-gonadal (HPG) axis are major players coordinating the development of immune system function and exerting powerful effects in the susceptibility to autoimmune disorders, including experimental autoimmune encephalomyelitis (EAE), the experimental model for multiple sclerosis (MS). In particular, GCs exert their beneficial immunosuppressive and anti-inflammatory effects in inflammatory disorders of the CNS, after binding to their cytoplasmic receptors (GRs). Here we review our work using transgenic (Tg) mice with a dysfunctional GR from early embryonic life on programming vulnerability to EAE. The GR-deficiency of these Tg mice confers resistance to active EAE induction. The interplay between GCs, proinflammatory mediators, gender and EAE is summarized. On the basis of our data, it does appear that exposure to a defective GR through development programs major changes in endogenous neuroendocrine and immune mechanisms controlling the vulnerability to EAE. These studies highlight the plasticity of the HPA-immune axis and its pharmacological manipulation in autoimmune diseases of the CNS.

Expression of antisense SnRK1 protein kinase sequence causes abnormal pollen development and male sterility in transgenic barley

A chimaeric gene was constructed comprising a wheat high molecular weight glutenin subunit gene promoter, a 304-bp sucrose non-fermenting-1-related (SnRK1) protein kinase sequence in the antisense orientation, and the cauliflower mosaic virus 35S RNA gene terminator. Transgenic barley plants containing the antisense SnRK1 chimaeric gene were produced by particle bombardment of barley immature embryos with the aim of obtaining plants expressing the antisense SnRK1 sequence in the seeds. Despite the fact that the promoter was expected to be active only in seeds, two independent transgenic lines were found to fail to transmit the transgene to the T1 generation. These T0 plants had matured and died before this was discovered, but subsequently four other independent transgenic lines were found to be affected in the same way. Cytological analysis of the pollen grains in these lines showed that about 50% were normal but the rest had arrested at the binucleate stage of development, were small, pear-shaped, contained little or no starch and were non-functional. The presence of antisense SnRK1 transcripts was detected in the anthers of the four lines analyzed and a ubiquitin promoter/UidA (Gus) gene, one of the marker genes codelivered with the antisense gene, was found to be expressed only in the abnormal pollen. Expression analyses confirmed that SnRK1 is expressed in barley anthers and that expression of one class of SnRK1 transcripts (SnRK1b) was reduced in the abnormal lines. All of the abnormal lines showed approximately 50% seed set, and none of the transgenes were detected in the T1 generation.

Identification of TSIX, encoding an RNA antisense to human XIST, reveals differences from its murine counterpart: implications for X inactivation

X inactivation is the mammalian method for X-chromosome dosage compensation, but some features of this developmental process vary among mammals. Such species variations provide insights into the essential components of the pathway. Tsix encodes a transcript antisense to the murine Xist transcript and is expressed in the mouse embryo only during the initial stages of X inactivation; it has been shown to play a role in imprinted X inactivation in the mouse placenta. We have identified its counterpart within the human X inactivation center (XIC). Human TSIX produces a >30-kb transcript that is expressed only in cells of fetal origin; it is expressed from human XIC transgenes in mouse embryonic stem cells and from human embryoid-body-derived cells, but not from human adult somatic cells. Differences in the structure of human and murine genes indicate that human TSIX was truncated during evolution. These differences could explain the fact that X inactivation is not imprinted in human placenta, and they raise questions about the role of TSIX in random X inactivation.

Impaired expression of the plastidic ferrochelatase by antisense RNA synthesis leads to a necrotic phenotype of transformed tobacco plants

Protoporphyrin IX is the last common intermediate of tetrapyrrole biosynthesis. The chelation of a Mg2+ ion by magnesium chelatase and of a ferrous ion by ferrochelatase directs protoporphyrin IX towards the formation of chlorophyll and heme, respectively. A full length cDNA clone encoding a ferrochelatase was identified from a Nicotiana tabacum cDNA library. The encoded protein consists of 497 amino acid residues with a molecular weight of 55.4 kDa. In vitro import of the protein into chloroplasts and its location in stroma and thylakoids confirm its close relationship to the previously described Arabidopsis thaliana plastid-located ferrochelatase (FeChII). A 1700-bp tobacco FeCh cDNA sequence was expressed in Nicotiana tabacum cv. Samsun NN under the control of the CaMV 35S promoter in antisense orientation allowing investigation into the consequences of selective reduction of the plastidic ferrochelatase activity for protoporphyrin IX channeling in chloroplasts and for interactions between plastidic and mitochondrial heme synthesis. Leaves of several transformants showed a reduced chlorophyll content and, during development, a light intensity-dependent formation of necrotic leaf lesions. In comparison with wild-type plants the total ferrochelatase activity was decreased in transgenic lines leading to an accumulation of photosensitizing protoporphyrin IX. Ferrochelatase activity was reduced only in plastids but not in mitochondria of transgenic plants. By means of the specifically diminished ferrochelatase activity consequences of the selective inhibition of protoheme formation for the intracellular supply of heme can be investigated in the future.

Double-stranded RNA-mediated silencing of genomic tandem repeats and transposable elements in the D. melanogaster germline

BACKGROUND

The injection of double-stranded RNA (dsRNA) has been shown to induce a potent sequence-specific inhibition of gene function in diverse invertebrate and vertebrate species. The homology-dependent posttranscriptional gene silencing (PTGS) caused by the introduction of transgenes in plants may be mediated by dsRNA. The analysis of Caenorhabditis elegans mutants impaired with dsRNA-mediated silencing and studies in plants implicate a biological role of dsRNA-mediated silencing as a transposon-repression and antiviral mechanism.

RESULTS

We investigated the silencing of testis-expressed Stellate genes by paralogous Su(Ste) tandem repeats, which are known to be involved in the maintenance of male fertility in Drosophila melanogaster. We found that both strands of repressor Su(Ste) repeats are transcribed, producing sense and antisense RNA. The Stellate silencing is associated with the presence of short Su(Ste) RNAs. Cotransfection experiments revealed that Su(Ste) dsRNA can target and eliminate Stellate transcripts in Drosophila cell culture. The short fragment of Stellate gene that is homologous to Su(Ste) was shown to be sufficient to confer Su(Ste)-dependent silencing of a reporter construct in testes. We demonstrated that Su(Ste) dsRNA-mediated silencing affects not only Stellate expression but also the level of sense Su(Ste) RNA providing a negative autogenous regulation of Su(Ste) expression. Mutation in the spindle-E gene relieving Stellate silencing also leads to a derepression of the other genomic tandem repeats and retrotransposons in the germline.

CONCLUSIONS

Homology-dependent gene silencing was shown to be used to inhibit Stellate gene expression in the D. melanogaster germline, ensuring male fertility. dsRNA-mediated silencing may provide a basis for negative autogenous control of gene expression. The related surveillance system is implicated to control expression of retrotransposons in the germline.

Decreased frequency of somatic hypermutation and impaired affinity maturation but intact germinal center formation in mice expressing antisense RNA to DNA polymerase zeta

To examine a role of DNA polymerase zeta in somatic hypermutation, we generated transgenic mice that express antisense RNA to a portion of mouse REV3, the gene encoding this polymerase. These mice express high levels of antisense RNA, significantly reducing the levels of endogenous mouse REV3 transcript. Following immunization to a hapten-protein complex, transgenic mice mounted vigorous Ab responses, accomplished the switch to IgG, and formed numerous germinal centers. However, in most transgenic animals, the generation of high affinity Abs was delayed. In addition, accumulation of somatic mutations in the V(H) genes of memory B cells from transgenic mice was decreased, particularly among those that generate amino acid replacements that enhance affinity of the B cell receptor to the hapten. These data implicate DNA polymerase zeta, a nonreplicative polymerase, in the process of affinity maturation, possibly through a role in somatic hypermutation, clonal selection, or both.

Identification of a novel beta-chemokine, MEC, down-regulated in primary breast tumors

Chemokines represent a family of low molecular weight secreted proteins that primarily function in the activation and migration of leukocytes. A number of additional functions of chemokines have also been identified including growth of tumor cells, angiogenesis and development. An iterative search for new chemokines has identified a cDNA that encodes a new member of the CC(beta) chemokine family. The gene has been named MEC, for mammary enriched chemokine. MEC expression was found at high levels in many mammary gland samples and was also detected at lower levels in several other epithelial-enriched tissues, such as salivary gland, colon, and prostate. Northern blot analysis demonstrates that MEC expression was highly reduced or eliminated in a majority of human breast tumors as compared to normal adjacent tissue. In situ hybridization demonstrates that MEC was abundantly expressed in normal mammary ductal epithelium, but expression was absent or reduced in various mammary tumor types of epithelial origin. These observations suggest that MEC may be useful as a diagnostic tool in oncology, and may play a role in regulating mammary carcinogenesis. The absence of MEC may also contribute to the host's immune response to tumors.

The Prader–Willi Syndrome Imprinting Center Activates the Paternally Expressed Murine Ube3a Antisense Transcript but Represses Paternal Ube3a

The imprinted UBE3A gene exhibits maternal-only expression in specific cell types in the brain, but exhibits biallelic expression in other cell types. UBE3A is located adjacent to a cluster of imprinted, paternally expressed genes that are known to be positively regulated by the Prader-Willi syndrome imprinting center (PWS-IC). Here, we examined the effect of the PWS-IC on the UBE3A locus. Using intersubspecific crosses, we found that deletion of the PWS-IC causes an upregulation of the paternal Ube3a allele. This indicates that unlike its positive effect on all the other paternally expressed transcripts in the region, the PWS-IC negatively regulates the levels of paternal UBE3A. Interestingly, we found that like the human UBE3A locus, the murine Ube3a locus includes an imprinted, paternally expressed antisense transcript. We show that this paternal antisense transcript is positively regulated by the PWS-IC. These results are consistent with a model in which the PWS-IC mediates activation and maintenance of paternal gene expression in the 15q11-q13 region, with repression of the paternal UBE3A gene occurring as an indirect result of expression of the antisense transcript.

Allelic IGF2R Repression Does Not Correlate with Expression of Antisense RNA in Human Extraembryonic Tissues

In the mouse, expression of an antisense Igf2r RNA (Air) is correlated with Igf2r repression on the paternal allele. One of the possible models for Igf2r repression could be through promoter competition or through the action of the Air RNA, in, e.g., transcriptional interference or repressor binding. These models predict the conservation of AIR RNA in human samples with monoallelic IGF2R expression and the production of AIR RNA in first-trimester human tissues. However, by strand-specific RT-PCR and by ribonuclease protection assay we have not detected any AIR RNA in first-trimester placental tissue samples, not even in samples that downregulate IGF2R expression in an allele-specific manner. This indicates that in contrast to the mouse, allelic IGF2R repression in the developing human placenta does not correlate with AIR expression.

[Construction of recombinant antisense RNA IgG2aVH region of murine systemic lupus erythematous]

OBJECTIVE

To construct recombinant plasmid of IgG2aVH region antisense RNA of systemic lupus erythematous.

METHODS

Total RNA was isolated from spleen cell of BWF1 mice. Using spleen cell total RNA as the template, We designed specific primers from A6.1 region sequences, and amplified the IgG2aVH region 375 bp DNA fragments by RT-PCR. The IgG2aVH cDNA was cloned by T/A and inserted into pcDNA 3.1 plasmid of vector.

RESULTS

The IgG2aVH antisense RNA plasmid expressing recombinant was identified by restriction enzyme digestion and DNA sequence analysis.

CONCLUSION

There is IgG2aVH gene in F1 mice spleen cell; the IgG2aVH antisense RNA expressing recombinants is constructed successfully.

Increased UV light sensitivity in transgenic Drosophila expressing the antisense XPD homolog

The XPD gene is required for excision repair of UV-damaged DNA and is an important component of nucleotide excision repair (NER). Mutations in the XPD gene generate the cancer-prone syndrome xeroderma pigmentosum, Cockayne's syndrome, and trichothiodystrophy. XPD is a component of the TFIIH transcription factor, which is essential for RNA polymerase II elongation. In this work, we report the construction of transgenic flies overexpressing the antisense RNA of the Drosophila melanogaster XPD homolog (DmXPD). These flies show an increased sensitivity to UV radiation compared with the wild-type. This is an expected phenotype if the XPD function is affected and indicates that the antisense approach may be an alternative in the study of TFIIH functions in Drosophila.

The endogenous retroviral insertion in the human complement C4 gene modulates the expression of homologous genes by antisense inhibition

Intron 9 contains the complete endogenous retrovirus HERV-K(C4) as a 6.4-kb insertion in 60% of human C4 genes. The retroviral insertion is in reverse orientation to the C4 coding sequence. Therefore, expression of C4 could lead to the transcription of an antisense RNA, which might protect against exogenous retroviral infections. To test this hypothesis, open reading frames from the HERV sequence were subcloned in sense orientiation into a vector allowing expression of a beta-galactosidase fusion protein. Mouse L cells which had been stably transfected with either the human C4A or C4B gene both carrying the HERV insertion (LC4 cells), and L(Tk-) cells without the C4 gene were transiently transfected either with a retroviral construct or with the wild-type vector. Expression was monitored using an enzymatic assay. We demonstrated that (1) HERV-K(C4) antisense mRNA transcripts are present in cells constitutively expressing C4, (2) expression of retroviral-like constructs is significantly downregulated in cells expressing C4, and (3) this downregulation is further modulated in a dose-dependent fashion following interferon-gamma stimulation of C4 expression. These results support the hypothesis of a genomic antisense strategy mediated by the HERV-K(C4) insertion as a possible defense mechanism against exogenous retroviral infections.

Comparative sequence analysis of plasmids pME2001 and pME2200 of methanothermobacter marburgensis strains Marburg and ZH3

Comparison of the updated complete nucleotide sequences of the two related plasmids pME2001 and pME2200 from the thermophilic archaeon Methanothermobacter marburgensis (formerly Methanobacterium thermoautotrophicum) strains Marburg and ZH3, respectively, revealed an almost identical common backbone structure and five plasmid-specific inserted fragments (IFs), four of which are flanked by perfect or nearly perfect direct repeats 25-52 bp in length. A 4354-bp minimal replicon was derived from the alignment of the two plasmids, which encodes one putative antisense RNA related to replication control and five open reading frames (ORFs) organized in two operons. The first operon consists of four ORFs, the third of which, i.e. ORF3, contains a helix-turn-helix motif and a purine NTP-binding motif often found in proteins involved in DNA metabolic processes. The database search results suggest that ORF3 might function as a replication initiator protein. The large putative Rep protein encoded by pME2001 was overexpressed in Escherichia coli as an N-terminal His-tagged version using pET28a and a compatible helper plasmid that coexpresses minor tRNAs, argU and ileX to compensate for codon usage difference. ORFs 1, 2, and 3 are organized in a sequence reminiscent of that described in E. coli plasmids of the R1 family, cop-tap-rep. ORF6 encoded by IF1, one of the pME2200-specific elements, showed significant similarity to ORF6 encoded by archaeal phage psiM2 of M. marburgensis strain Marburg and may confer the apparent immunity of its host strain ZH3 to infection by phage psiM2. Our data indicate that M. marburgensis plasmids may evolve by a series of gene duplication and excision events.

Adenovirus-mediated expression of antisense RNA transcripts complementary to pig alpha(1,3) galactosyltransferase mRNA inhibits expression of Gal alpha(1,3) Gal epitope

AIM

To examine the effects of the expression of antisense RNA transcripts complementary to the pig alpha(1,3) galactosyltransferase [alpha(1,3)GT]mRNA on the expression of Gal alpha(1,3) Gal structure (gal epitope) in cultured cell lines.

METHODS

Human adenoviral vectors were used to mediate the expression of antisense RNA. The expression levels of H blood group antigens and gal epitopes were analyzed by flow cytometry using FITC-UEA-I and FITC-GS-IB4 lectins, respectively.

RESULTS

Recombinant adenoviruses, Ad5anti-sGT600 and Ad5-anti-sGT1100, which express antisense RNA complementary to different regions of the pig alpha(1,3) GT mRNA, were constructed and used to infect cell line of NIH3T3. The results showed about 30% reduction in the expression level of gal epitopes on the surface of NIH3T3 cells. In addition, co-expression of human secretor type alpha(1,2) fucosyltransferase [alpha(1,2)FT]cDNA and antisense RNA complementary to the pig alpha(1,3) GT mRNA led to a further reduction in the gal epitope level.

CONCLUSION

Recombinant adenoviruses, Ad5anti-sGT600 and Ad5anti-sGT1100, are effective to down-regulate the gal epitope expression.

Suppression of manganese superoxide dismutase augments sensitivity to radiation, hyperthermia and doxorubicin in colon cancer cell lines by inducing apoptosis

Increased expression of manganese superoxide dismutase (Mn-SOD), one of the mitochondrial enzymes involved in the redox system, has been shown to diminish the cytotoxic effects of several anti-cancer modalities, including tumour necrosis factor-alpha, ionizing radiation, certain chemotherapeutic agents and hyperthermia. We asked if Mn-SOD is a potential target to augment the sensitivity of cancer cells to various anti-cancer treatments and for this we established stable Mn-SOD antisense RNA expressing cell clones from two human colon cancer cell lines, HCT116 (p53 wild-type) and DLD1 (p53 mutant-type). Suppression of Mn-SOD in HCT116 was accompanied by an increased sensitivity to radiation, hyperthermia and doxorubicin, as compared with findings in controls. The mitochondrial permeability transition, as measured by a decrease of the mitochondrial transmembrane potential was more intensely induced by radiation in HCT116 antisense clones than in the control, an event followed by a greater extent of DNA fragmentation. Apoptosis was also induced by hyperthermia more intensely in HCT116 antisense clones than in the control. On the other hand, DLD1 antisense clones did not exhibit any enhancement of sensitivity to any of these treatments. These data support the possibility that inhibition of Mn-SOD activity renders colon cancer cells with wild-type p53 susceptible to apoptosis induced by radiation, hyperthermia and selected anti-cancer drugs. Therefore, we suggest that Mn-SOD could be a target molecule to overcome the resistance to anti-cancer treatments in some colon cancer cells carrying wild-type p53.

Expression of c-erbB receptors, heregulin and oestrogen receptor in human breast cell lines

Members of the c-erbB family have been implicated in poor prognosis in breast cancer. Given the propensity for heterodimerisation within the erbB family, the pattern of co-expression of these receptors is likely to be as functionally important as aberrant expression of any given receptor alone. Therefore, the patterns of expression of the receptors, epidermal growth factor receptor (EGF-R), c-erbB-2, c-erbB-3, c-erbB-4, and one of the erbB ligands, heregulin (HRG), were examined in normal and malignant breast cell lines and compared with expression of oestrogen receptor (ER), a classical indicator of good prognosis. There was an inverse correlation between ER and EGF-R mRNA levels, as previously described, but no correlation between either of these receptors and c-erbB-2. c-erbB-3 expression was positively correlated with ER. In contrast, HRG expression was inversely related to ER. Expression of antisense-ER resulted in increased EGF-R mRNA, demonstrating a functional link between the expression of these 2 genes, however, there was no significant change in c-erbB-2 or c-erbB-3 mRNA, suggesting that ER is not directly involved in control of expression of these genes. A comparison of individual erbB receptors and HRG revealed that the majority of lines expressing increased levels of c-erbB-2 also expressed elevated levels of c-erbB-3 mRNA, and none of the cell lines that expressed both c-erbB-2 and either c-erbB-3 or c-erbB-4 expressed the ligand HRG. In summary, the levels of expression of c-erbB-1, -2, -3, and -4 varied in this series of breast cell lines, and the pattern of expression and the relationship of each growth factor receptor to the expression of ER was quite distinct. The lack of expression of HRG in cell lines that express receptors may be indicative of paracrine interactions between erbB ligands and their cognate receptors and may suggest that the ligand and receptors are expressed in different subtypes of breast epithelial cells from which the cell lines are derived.

Multiple S gene family members including natural antisense transcripts are differentially expressed during development of maize flowers

Within the large Brassica S gene family, SLG (S locus glycoprotein) and SRK (S locus receptor kinase) participate to the control of pollen-stigma self-incompatibility. In the self-compatible species maize, S gene family members are predominantly expressed in vegetative organs but are also expressed to a lesser extent in the stigma (silk). To determine if the expression of any S gene family members correlates with female receptivity, we analyzed their expression in developing maize silks. We show that a large family of maize S transcripts is expressed in developing silks. Surprisingly, we isolated a cDNA complementary to a large portion of the antisense strand of the maize receptor kinase S domain. Rapid amplification of cDNA ends (RACE)-polymerase chain reaction, RNase protection, and Northern hybridization with single-stranded riboprobes confirmed that natural antisense S transcripts exist in leaves and seedling shoots and in all sexual tissues tested except mature pollen. These natural antisense S transcripts co-exist with several less abundant sense S transcripts. The accumulation of sense and antisense S transcripts is differentially regulated during pollen and silk development. Thus, these results support a role for S gene family members in sexual tissue development and/or compatible pollination and reveal a new level of complexity in the regulation and function of the S gene family in maize.

Downregulation of the urokinase-type plasminogen activator receptor through inhibition of translation by antisense oligonucleotide suppresses invasion of human glioblastoma cells

We previously showed that downregulation of the urokinase-type plasminogen activator receptor (uPAR) in the SNB19 human glioblastoma cell line by the stable transfection of a plasmid expressing a 300 bp antisense sequence to the 5' end of the uPAR gene produced a decrease in the amount of target mRNA. In a more recent study, we found that adenovirus-mediated transduction (Ad-uPAR) of the same uPAR antisense gene construct in SNB19 cells also downregulated uPAR protein levels. We report here that Ad-uPAR-transfected SNB19 cells produced the same amounts of target uPAR mRNA but significantly less protein by in vitro translation and by in situ [35S] labeling compared to Ad-CMV vector-transfected and mock-transfected cells. This antisense construct also inhibited glioblastoma cell invasion confirming previous results. We conclude that downregulation of uPAR by this antisense gene construct results from inhibition of protein translation.

Cytoplasmic dynein heavy chain is an essential gene product in Dictyostelium

We describe here three different approaches to perturb cytoplasmic dynein heavy chain (DHC) gene function in Dictyostelium: integration of a marker into the heavy chain coding sequence by homologous recombination to disrupt transcription, expression of antisense RNA to inhibit translation, and expression of a 158 kDa amino-terminal coding region to perturb the native protein organization. By homologous recombination, we fail to obtain cells that lack an intact DHC gene product. Cells containing antisense orientation plasmids (but not sense) appear to die 4 to 6 days following transformation. Plasmids designed to overexpress an amino-terminal region of the DHC result in substantially reduced transformation efficiency. When expressed at low levels, the truncated amino-terminal product appears capable of dimerizing with an intact heavy chain or with itself, essentially producing a cargo-binding domain lacking mechanochemical activity. This, in turn, likely competes with the native protein's function. These three approaches taken together indicate that the dynein heavy chain is an essential gene in Dictyostelium.

[The effects of cyclin E on the growth and other cell cycle related genes of breast carcinoma cells MCF-7]

OBJECTIVE

To investigate the effects of cyclin E in high and low expression on the cell growth and other cell cycle associated genes of MCF-7 cells.

METHODS

Eukaryotic expression vehicles of sense and antisense cyclin E were constructed and transferred into the MCF-7 cell line using lipofectAMINE. The integration and expression of cyclin E were conformed by Southern and Western blot. The cells growth was observed and the changes in cell cycle were analyzed by flow cytometry. The expression of other cell cycle associated genes was assayed using Western blot.

RESULTS

A high expression of cyclin E enabled to promote the cell growth and DNA synthesis and accelerated the proceeding of G(1) phase to S phase, It also promoted the phosphorylatin of pRB and up-regulate the expression of p27 while a low expression of cyclin E showed an opposite effect.

CONCLUSION

Different expression of cyclin E enables to affect growth of MCF-7 cell by the changes of cell cycle related genes.

Inhibition of human immunodeficiency virus type 1 by packageable, multigenic antisense RNA

Viral-based vectors can provide an efficient delivery mechanism for stable expression of antisense RNA. To enhance and propagate the antiviral effect of antisense RNA, two novel human immunodeficiency virus type 1 (HIV-1)-based vector DNAs, designated as pMAG7 and pMAG19, were constructed which contained HIV-1 cis-acting packaging elements and produced multigenic HIV-1 antisense RNA that could target the entire pol, env, vif, vpu, vpr, rev, and tat and portions of gag and nef. The two DNAs were identical except that pMAG19 had additional gag coding sequences. Cotransfection of pMAG DNA and infectious, cloned HIV-1 DNA in 293 cells inhibited virus production (81%-98% reduction in reverse transcriptase activity) of various T cell-tropic and macrophage-tropic clade B isolates, such as NL4-3, YU-2, and JR-CSF. In addition, virion-associated pMAG antisense RNA was detected in residual virus particles produced by pNL4-3 in the presence of pMAG7 DNA, and the antisense sequences were stably transferred by infection of 174 x CEM cells. The results suggest that pMAG DNA may confer broad protection against HIV-1 by reducing initial virus burden due to antisense RNA and subsequent virus spread by propagation of antisense sequences along with wild-type virus.