Biomedical subjects

A Bukovsky

Publications and source records attributed to A Bukovsky.

At least 19 recordsLinked to original sources

PubMed2001

Association of mesenchymal cells and immunoglobulins with differentiating epithelial cells.

BACKGROUND: Mesenchymal-epithelial interactions play an important role in the physiology and pathology of epithelial tissues. Mesenchymal cells either associate with epithelium basement membrane [pericytes and perivascular monocyte-derived cells (MDC)] or reside within epithelium (MDC and T cells). Although intraepithelial mesenchymal cells were suggested to contribute to the epithelium physiology, their association with particular steps in differentiation of epithelial cells, interactions among themselves, and their fate remain unclear. We studied epitopes of mesenchymal cells and their products (immunoglobulins) in stratified epithelium of uterine ectocervix, which is one of the prototypes of complete cellular differentiation from stem into the aged cells. RESULTS: Perivascular CD14 primitive MDC associated with basal (stem) epithelial cells. Thy-1 pericytes of microvasculature secreted intercellular vesicles, which associated with Ki67 postmitotic epithelial cells expressing MHC class I. Intraepithelial T cells showed an association with veiled type MDC [dendritic cell (DC) precursors] among parabasal cells, and exhibited fragmentation after entering intermediate (mature) epithelial layers. Mature DC secreted CD68 and exhibited fragmentation after reaching mid intermediate layers. Binding of IgM was detected at the top of each layer: in the upper parabasal, upper intermediate, and most surface epithelial cells. IgG was confined to the entire superficial layer. CONCLUSIONS: These data suggest that the phylogenetically and ontogenetically developed hierarchy of mesenchymal cells (MDC, pericytes, T cells) and immunoglobulins (IgM, IgG) accompanies differentiation of epithelial cells from immature into the mature and aged phenotype. Further studies of an involvement of mesenchymal cells in the regulation of tissue homeostasis may bring novel approaches to the prevention and therapy of tissue dysfunctions characterized by permanent tissue immaturity (muscular dystrophy) or accelerated aging (degenerative diseases).

Apoptosis↗

PubMed2001

A new-generation stable inducible packaging cell line for lentiviral vectors.

We have successfully generated and characterized a stable packaging cell line for HIV-1-based vectors. To allow safe production of vector, a minimal packaging construct carrying only the coding sequences of the HIV-1 gag-pol, tat, and rev genes was stably introduced into 293G cells under the control of a Tet(o) minimal promoter. 293G cells express the chimeric Tet(R)/VP16 trans-activator and contain a tetracycline-regulated vesicular stomatitis virus protein G (VSV-G) envelope gene. When the cells were grown in the presence of tetracycline the expression of both HIV-1-derived and VSV-derived packaging functions was suppressed. On induction, approximately 50 ng/ml/24 hr of Gag p24 equivalent of vector was obtained. After introduction of the transfer vector by serial infection, vector could be collected for several days with a transduction efficiency similar or superior to that of vector produced by transient transfection both for dividing and growth-arrested cells. The vector could be effectively concentrated to titers reaching 10(9) transducing units/ml and allowed for efficient delivery and stable expression of a GFP transgene in the mouse brain. The packaging cell line and all vector producer clones described here were shown to be free from replication-competent recombinants, and from recombinants between packaging and vector constructs that transfer the viral gag-pol genes. The packaging cell line and the assays developed will advance lentiviral vectors toward the stringent requirements of clinical applications.

Animals↗

PubMed2001

Signal transduction through the Ras/Erk pathway is essential for the mycoestrogen zearalenone-induced cell-cycle progression in MCF-7 cells.

Zearalenone is a naturally occurring estrogenic contaminant of moldy feeds and is present in high concentrations in dairy products and cereals. Zearalenone was postulated to contribute to the overall estrogen load of women, but the mechanisms of its action are not known. We demonstrated that zearalenone could stimulate the growth of estrogen receptor-positive human breast carcinoma cell line MCF-7. In addition, zearalenone functioned as an antiapoptotic agent by increasing the survival of MCF-7 cell cultures undergoing apoptosis caused by serum withdrawal. Treatment of these cells with 100 nM zearalenone induced cell-cycle transit after increases in the expression of c-myc mRNA and cyclins D1, A, and B1 and downregulation of p27(Kip-1). G(1)/G(2)-phase kinase activity and phosphorylation of the retinoblastoma gene product was also evident. Flow cytometric analysis demonstrated entry of cells into the S and G(2)/M phases of the cell cycle, and phosphorylation of histone H3 occurred 36 h after zearalenone treatment. Ectopic expression of a dominant-negative p21(ras) completely abolished the zearalenone-induced DNA synthesis in these cells, and the specific inhibitor PD98059 for mitogen/extracellular-regulated protein kinase kinase arrested S-phase entry induced by zearalenone. These data suggest that the mitogen-activated protein kinase signaling cascade is required for zearalenone's effects on cell-cycle progression in MCF-7 cells. Given the presence of this mycotoxin in cereals, milk, and meat, the possibility that zearalenone is a potential promoter of breast cancer tumorigenesis should be investigated further. Mol. Carcinog. 30:88-98, 2001.

Adenoviridae↗

PubMed2001

The role of the host-tumor interface and cell hybridization in invasive cancer.

Available data indicate that growth of invasive tumors is enhanced by homeostatic mechanisms of the host involved in normal tissue regeneration and repair. To achieve this, malignant cells may (i) induce degeneration of normal cells at the host-tumor interface, (ii) hybridize in situ with activated host stem cells, required for replacement of lost mature tissue cells, (iii) the resulting malignant/normal cell hybrids may exhibit an antigenic similarity to normal cells, (iv) thereby preventing recognition by the immune system, (v) and exploiting normal mechanisms of tissue regeneration by the host. In addition, primary cancers with allotypic determinants may utilize other homeostatic mechanisms evolved in mammals to promote fetal allograft survival. They may have a potential to grow in another (secondary) host. Novel approaches to cancer prevention and control may depend on a better understanding of the mechanisms by which normal cellular growth are controlled, and hybridization prevented.

Animals↗

PubMed2001

Estrogen, progesterone, and androgen receptor expression in levator ani muscle and fascia.

Previous studies have reported controversial data on estrogen receptor (ER) expression in levator ani muscle. We investigated ER expression in levator ani muscle and fascia and compared it with the expression of progesterone receptor (PR) and androgen receptor (AR). The study included 55 women undergoing surgery for gynecological (asymptomatic, n = 10) or urogynecological conditions (symptomatic, n = 45). The asymptomatic and 21 of the symptomatic women received no hormone replacement therapy (HRT). The remaining 24 symptomatic women received some form of HRT. Biopsies were taken from the levator ani muscle and the overlying fascia, and quantitative measurements of immunohistochemical staining by image analysis were made. None of the levator ani muscle samples showed any evidence of nuclear ER expression in striated muscle fibers, but some cells in the muscular stroma did express ER. However, PR and AR expression was found in both muscle and stromal cells. Levator ani fascia showed nuclear ER, PR, and AR expression to varying degrees. There was a significant increase (p < 0.03) in ER expression in levator ani fascia of symptomatic patients without HRT when compared with asymptomatic age-matched women. The ER expression was significantly lower (p < 0.001) in postmenopausal symptomatic women receiving long-term estrogen replacement compared with age-matched women without HRT. Our data indicate that ER expression is significantly higher in symptomatic women compared with age-matched asymptomatic females. However, long-term estrogenization causes significant decrease of ER expression.

Adult↗

PubMed2001

Multifaceted regulation of cell cycle progression by estrogen: regulation of Cdk inhibitors and Cdc25A independent of cyclin D1-Cdk4 function.

Estrogens induce proliferation of estrogen receptor (ER)-positive MCF-7 breast cancer cells by stimulating G(1)/S transition associated with increased cyclin D1 expression, activation of cyclin-dependent kinases (Cdks), and phosphorylation of the retinoblastoma protein (pRb). We have utilized blockade of cyclin D1-Cdk4 complex formation through adenovirus-mediated expression of p16(INK4a) to demonstrate that estrogen regulates Cdk inhibitor expression and expression of the Cdk-activating phosphatase Cdc25A independent of cyclin D1-Cdk4 function and cell cycle progression. Expression of p16(INK4a) inhibited G(1)/S transition induced in MCF-7 cells by 17-beta-estradiol (E(2)) with associated inhibition of both Cdk4- and Cdk2-associated kinase activities. Inhibition of Cdk2 activity was associated with delayed removal of Cdk-inhibitory activity in early G(1) and decreased cyclin A expression. Cdk-inhibitory activity and expression of both p21(Cip1) and p27(Kip1) was decreased, however, in both control and p16(INK4a)-expressing cells 20 h after estrogen treatment. Expression of Cdc25A mRNA and protein was induced by E(2) in control and p16(INK4a)-expressing MCF-7 cells; however, functional activity of Cdc25A was inhibited in cells expressing p16(INK4a). Inhibition of Cdc25A activity in p16(INK4a)-expressing cells was associated with depressed Cdk2 activity and was reversed in vivo and in vitro by active Cdk2. Transfection of MCF-7 cells with a dominant-negative Cdk2 construct inhibited the E(2)-dependent activation of ectopic Cdc25A. Supporting a role for Cdc25A in estrogen action, antisense CDC25A oligonucleotides inhibited estrogen-induced Cdk2 activation and DNA synthesis. In addition, inactive cyclin E-Cdk2 complexes from p16(INK4a)-expressing, estrogen-treated cells were activated in vitro by treatment with recombinant Cdc25A and in vivo in cells overexpressing Cdc25A. The results demonstrate that functional association of cyclin D1-Cdk4 complexes is required for Cdk2 activation in MCF-7 cells and that Cdk2 activity is, in turn, required for the in vivo activation of Cdc25A. These studies establish Cdc25A as a growth-promoting target of estrogen action and further indicate that estrogens independently regulate multiple components of the cell cycle machinery, including expression of p21(Cip1) and p27(Kip1).

Adenoviridae↗

PubMed2000

Postnatal androgenization induces premature aging of rat ovaries.

In the present paper, we report that ovaries of adult rats treated with testosterone propionate (TP) on a critical postnatal Day 5 exhibit histologic and immunohistochemical findings which resemble those of the anovulatory ovaries in middle-aged female rats. The sterile rat model has been long known whereas ovarian failure seems to be a reason for anovulation with normal hypothalamo-pituitary-gonadotropin background. Appropriate function of ovarian steroidogenic cells is also regulated by mesenchymal cells. To characterize the ovarian failure, we studied the histology, luteinizing hormone receptor (LHR) expression, and characterized changes of vascular pericytes, T cells, and dendritic cells in ovarian steroidogenic compartments consisting of interstitial cells (ISC) of ovarian interstitial glands, and granulosa and theca interna cells of ovarian follicles. Normal adult ovaries contained 63% of mature interstitial glands. The mature ISC exhibited moderate cytoplasmic and strong surface LHR expression and fine (<5 micrometer) cytoplasmic vacuoles (ISC of 'luteal type'). They originated from young ISC of 'thecal type,' which exhibited strong cytoplasmic LHR expression. Remaining 37% were aged interstitial glands, which consisted of aged ISC (increased cytoplasmic vacuolization, nuclear pyknosis, and reduced surface LHR expression) and regressing ISC (weak cytoplasmic and no surface LHR expression). However, no mature ISC of 'luteal type' were detected in anovulatory ovaries of adult rats (45- and 60-day-old) injected with TP (100 or 500 microgram) on postnatal Day 5 (TP rats). Their ovaries contained 96% of aged interstitial glands with aged and regressing ISC. Remaining 4% were abnormal interstitial glands with direct transition of young ISC of 'thecal type' into aged ISC (young/aged glands). Lack of mature ISC, and similar amount of aged (96%) and young/aged interstitial glands (4%) was also detected in anovulatory ovaries of untreated persistently estrous middle-aged (10-month-old) females (aging PE rats). The aging process in TP and aging PE rats was accompanied by regression of vascular pericytes, T cells, and dendritic cells within the interstitial glands. In addition, anovulatory ovaries of TP rats and aging PE females contained mature follicles exhibiting LHR overexpression by granulosa cells, and aged (cystic) follicles with reduced layers of granulosa cells lacking LHR expression. In contrast, when the rats were injected with 500 microgram of TP later, on postnatal Day 10, the adult females exhibited estrous cycles and normal ovaries with corpora lutea. These results show that injection of TP during the critical postnatal period causes a lack of mature and preponderance of aged ISC in adult ovaries, accompanied by degeneration of mesenchymal cells. We suggest that mesenchymal cells regulate qualitative aspects of tissue-specific cells, and this function of mesenchymal cells is programmed during the critical period of development.

Androgens↗

PubMed2000

Dominant role of monocytes in control of tissue function and aging.

We propose that monocyte-derived cells regulate expression of epitopes of specific tissue cells, and in that way control recognition of tissue cells by autoreactive T lymphocytes and autoantibodies. Such T cells and antibodies are suggested to participate in stimulation of tissue cell differentiation. This may ultimately result in the aging and degeneration of tissue cells. By the end of their adaptation in early ontogeny, the monocyte-derived cells are supposed to encounter the most differentiated tissue cells in a tissue specific manner, and then prevent tissue cells to differentiate beyond the encoded state. Retardation or acceleration of certain tissue differentiation during adaptation results in a rigid and permanent alteration of this tissue function. The ability of monocytes to preserve tissue cells in the functional state declines with age, and this is accompanied by functional decline of various tissues within the body, and an increased incidence of degenerative diseases.

Aging↗

PubMed1999

Regression of endometrial explants in a rat model of endometriosis treated with the immune modulators loxoribine and levamisole.

OBJECTIVE: To investigate the effects of the immune modulators levamisole and loxoribine in a rat model of endometriosis. DESIGN: Prospective, placebo-controlled study. SETTING: Hospital-based research facility. ANIMAL(S): Nineteen rats with experimentally induced endometriosis. INTERVENTION(S): Rats were treated with three weekly intraperitoneal injections of levamisole (2 mg per rat; n = 6), loxoribine (1 mg per rat; n = 6), or saline (control; n = 7) and killed 8 weeks after treatment. MAIN OUTCOME MEASURE(S): Histologic and immunohistochemical analysis of endometriotic explants. RESULT(S): The loxoribine-treated group showed marked regression of both epithelial and stromal components. Epithelial regression was noted in the control group, but the epithelium was strikingly preserved in the levamisole group. There were significantly greater numbers of dendritic cells in the explants of animals treated with loxoribine and levamisole. The number of natural killer cells was significantly reduced in loxoribine-treated explants. CONCLUSION(S): Loxoribine, a potent immunomodulatory drug, appeared to cause regression in both stromal and epithelium components in a rat model of endometriosis. Further, specific cell-mediated immune responses in this model of endometriosis were elucidated.

Adjuvants, Immunologic↗

PubMed1999

Thy-1 differentiation protein and monocyte-derived cells during regeneration and aging of human placental villi.

PROBLEM: The classification of placental villi was reviewed, and regeneration of villous trees in mature human placentae was examined. METHOD OF STUDY: Expression of Thy-1 by placental fibroblasts and pericytes, and markers of endothelial cells and monocyte-derived cells were studied by immunohistochemistry and image analysis. RESULTS: Villous regeneration consists of: (i) dedifferentiation of mature ramuli into young stem villi producing mesenchymal villi; (ii) differentiation of mesenchymal villi into immature intermediate villi; and (iii) differentiation of immature intermediate villi into transitory intermediate villi, branching into the precursors of mature intermediate and terminal villi. These processes are associated with dedifferentiation and redifferentiation of placental monocyte-derived cells. Significant changes of Thy-1 expression by fibroblasts and pericytes accompany aging and degeneration, as well as regeneration of placental villi. CONCLUSIONS: Villous aging and degeneration in normal mature human placenta is compensated by regeneration of villous trees. Lack of villous regeneration may cause chronic fetal distress, due to the increasing demands of the growing fetus on the remaining terminal villi.

Cellular Senescence↗

PubMed1998

Expression of G1 cyclins and cyclin-dependent kinase-2 activity during terminal differentiation of cultured human trophoblast.

Cyclin-dependent kinases (Cdks) and their cyclin partners regulate mammalian cell proliferation and withdrawal from the cell cycle and, as such, control differentiation in many tissues. Studies were undertaken to examine the roles of cell cycle proteins in differentiating cytotrophoblasts. Cyclin E gene and protein expression was down-regulated after 24 h in cultured trophoblasts. Cdk2-associated kinase activity was decreased after 96 h in culture as was the amount of cyclin E in complexes with Cdk2; however, levels of the Cdk inhibitor, p27Kip1, were significantly increased. In freshly isolated trophoblasts and in 24-h cultures, the retinoblastoma gene product (pRb) was found in both the active and inactive forms, yet only hypophosphorylated, active pRb was present in syncytiotrophoblast. Thus, inactivation of Cdk2 through cyclin E down-regulation and increased p27Kip1 expression leads to an accumulation of active pRb in syncytiotrophoblast. Prevention of entry into S phase by hypophosphorylated pRb may allow trophoblasts to respond to signals that potentiate differentiation. Our studies suggest that regulation of G1-phase Cdk activity may be involved in the terminal differentiation process of cytotrophoblasts.

Blotting, Northern↗

PubMed1998

Self-inactivating lentivirus vector for safe and efficient in vivo gene delivery.

In vivo transduction of nondividing cells by human immunodeficiency virus type 1 (HIV-1)-based vectors results in transgene expression that is stable over several months. However, the use of HIV-1 vectors raises concerns about their safety. Here we describe a self-inactivating HIV-1 vector with a 400-nucleotide deletion in the 3' long terminal repeat (LTR). The deletion, which includes the TATA box, abolished the LTR promoter activity but did not affect vector titers or transgene expression in vitro. The self-inactivating vector transduced neurons in vivo as efficiently as a vector with full-length LTRs. The inactivation design achieved in this work improves significantly the biosafety of HIV-derived vectors, as it reduces the likelihood that replication-competent retroviruses will originate in the vector producer and target cells, and hampers recombination with wild-type HIV in an infected host. Moreover, it improves the potential performance of the vector by removing LTR sequences previously associated with transcriptional interference and suppression in vivo and by allowing the construction of more-stringent tissue-specific or regulatable vectors.

3T3 Cells↗

PubMed1997

Inhibition of early and late events of the HIV-1 replication cycle by cytoplasmic Fab intrabodies against the matrix protein, p17.

BACKGROUND: The HIV-1 matrix (MA) protein, p17, contains two subcellular localization signals that facilitate both nuclear import of the viral preintegration complex early during infection and virus particle assembly late in infection. The dual role of MA in both the afferent and efferent arms of the HIV-1 life cycle makes it an important target for intracellular immunization-based gene therapy strategies. MATERIALS AND METHODS: Here we report, using a new bicistronic vector, that an intracellular Fab antibody, or Fab intrabody, directed against a carboxy-terminal epitope of MA from the Clade B HIV-1 genotype, can inhibit HIV-1 infection when expressed in the cytoplasm of actively dividing CD4+ T cells. RESULTS: Marked inhibition of proviral gene expression occurred when single-round HIV-1 CAT virus was used for infections. In challenge experiments using both laboratory strains and syncytium-inducing primary isolates of HIV-1, a substantial reduction in the infectivity of virions released from the cells was also observed. CONCLUSIONS: This novel strategy of simultaneously blocking early and late events of the HIV-1 life cycle may prove useful in clinical gene therapy approaches for the treatment of HIV-1 infection and AIDS, particularly when combined with genetic or pharmacologic-based strategies that inhibit other HIV-1 target molecules simultaneously.

Animals↗

PubMed1996

Glycoprotein incorporation and HIV-1 infectivity despite exchange of the gp160 membrane-spanning domain.

We have examined the role of the membrane-anchoring domain of the HIV-1 glycoproteins in viral glycoprotein function, glycoprotein incorporation, and viral infectivity. For this purpose, we initially exchanged the entire membrane-spanning region with that from a cellular glycoprotein (CD22). Subsequently, the strictly conserved arginine in the central position of the transmembranal alpha-helix was replaced by a neutral residue (R696 --> I696). We have further examined the requirements within the cytoplasmic C-terminus for glycoprotein incorporation and replaced this region of gp160 with the long cytoplasmic C-terminus (118 amino acids) from CD22. Our results show that the specific amino acid sequence of the membrane-spanning region of gp160 is not necessary for viral infectivity, thus making it unlikely that this region is specifically involved in membrane fusion, in glycoprotein incorporation, or in infectivity of the cell lines tested. In contrast, recombinant gp160 with the CD22 C-terminal region, although present at the cell surface and membrane fusion-competent, was excluded from incorporation into particles. This could indicate that steric exclusion, and no pseudotyping, occurs when the heterologous, cytoplasmic C-terminal region is too long and not fitting.

Amino Acid Sequence↗

PubMed1996

Activation of mitogen-activated protein kinases by gonadotropins and cyclic adenosine 5'-monophosphates in porcine granulosa cells.

A variety of growth factors and guanosine triphosphate (GTP) binding protein-linked receptors are known to activate mitogen activated protein kinases (MAPK); however, no evidence exists demonstrating activation of the MAPK pathway by glycoprotein hormones. Using porcine granulosa cells (PGC), we show that physiological concentrations of LH and FSH increase enzymatic activity 1) of p44MAPK extracellular regulated kinase 1 (ERK1) but not that of p42MAPK (ERK2) in the cytosol and 2) of both ERK1 and ERK2 in the nucleus. Cytosolic ERK1 was activated by LH more rapidly than by FSH. Cyclic AMP increased kinase activities of both ERK1 and ERK2 in the cytoplasm as well as in the nucleus. Activation of ERK1 by gonadotropins and cAMP was accompanied by increased tyrosine phosphorylation of the kinase. Immunohistochemical studies demonstrated predominantly cytoplasmic staining for MAPK in untreated PGC cultures whereas treatment with gonadotropins led to increased nuclear immunoreactivity indicating translocation of MAPK to the nucleus. The translocation as well as increase in nuclear ERK1 and ERK2 was delayed and coincided with a decrease in cytosolic ERK1 activity. Epidermal growth factor (EGF) increased ERK1 and ERK2-associated kinase activity 7-8-fold in the cytoplasm of PGC, while kinase activity of cytoplasmic ERK1 was enhanced 3-4-fold by LH, FSH, or cAMP. In summary, we have for the first time demonstrated that gonadotropins (and cAMP) can activate MAPK in appropriate target cells.

Animals↗

PubMed1996

Lack of integrase can markedly affect human immunodeficiency virus type 1 particle production in the presence of an active viral protease.

The Gag-Pol polyprotein of human immunodeficiency virus type 1 is not required for efficient viral particle assembly or release. However, in this report we demonstrate that the synthesis of a truncated Gag-Pol precursor due to a premature termination codon in pol can reduce the ability of a full-length provirus to direct the formation of viral particles. Marked effects on particle production were seen when premature termination codons were introduced into the integrase (IN)-coding region. By contrast, a mutant which lacked both IN and reverse transcriptase (RT) formed particles with normal efficiency. Particle production by IN mutants was restored to wild-type levels when a second premature termination codon was introduced at the 5' end of the RT-coding sequence. Particle formation was similarly restored by a second site mutation in the viral protease (PR) gene which prevented proteolytic processing of the Gag polyprotein. Finally particle formation was restored in the presence of A77003, a specific inhibitor of human immunodeficiency virus type 1 PR. These results suggest that the effects of a lack of IN sequences on particle formation require the synthesis of a Gag-Pol precursor which contains RT sequences and are due to inappropriate PR activity.

Animals↗

PubMed1995

Expression of cell cycle regulatory proteins (p53, pRb) in the human female genital tract.

PURPOSE: Recent studies have shown that proliferation and differentiation of various cell types is regulated by cell-cycle-related proteins, such as protein p53 and retinoblastoma protein pRb. METHODS: Three monoclonal antibodies to p53 (PAb240, PAb421, and PAb1801) and 3H9 monoclonal antibody to pRb were utilized for localization of proteins by peroxidase immunohistochemistry in frozen tissue sections. RESULTS: Nuclear and nucleolar p53 expression was detected in nondividing and relatively stable cells, e.g., oocytes in primordial follicles and granulosa lutein cells. On the other hand, strong cytoplasmic p53 expression was detected in proliferating and low differentiated epithelial cells of the ovarian surface epithelium, amnion, endocervix and ectocervix, indicating enhanced p53 synthesis. Not all three p53 antibodies reacted with each tissue, perhaps due to structural and conformational changes in the p53 molecule, accompanying p53 association with other proteins, e.g., tissue specific transcription factor interactions. pRb expression was usually restricted to the cell nuclei and nucleoli. However, glandular cells of the female reproductive tract showed cytoplasmic pRb expression in juxtaluminal (secretory) segments of cells, a feature not previously described in any cell type. p53 and pRb immunoreactivities declined with advanced differentiation of cells. No p53 or pRb was detected in placental syncytiotrophoblast or terminally differentiated squamous epithelial cells. CONCLUSION: Our data indicate that large quantities of p53 are synthesized in cells leaving the cell cycle and entering differentiation. Except in glandular cells, the pRb expression is confined to the cell nuclei and nucleoli. A unique cytoplasmic expression of pRb in juxtaluminal segments of glandular cells suggests a role for pRb in human female fertility and conception.

Antibodies, Monoclonal↗

PubMed1995

Rescue of human immunodeficiency virus type 1 matrix protein mutants by envelope glycoproteins with short cytoplasmic domains.

The matrix (MA) protein of human immunodeficiency virus type 1 (HIV-1) forms the outer protein shell directly underneath the lipid envelope of the virion. The MA protein has a key role in different aspects of virus assembly, including the incorporation of the HIV-1 Env protein complex, which contains a transmembrane glycoprotein with an unusually long cytoplasmic tail. In this study, we compared the abilities of HIV-1 MA mutants to incorporate Env protein complexes with long and short cytoplasmic tails. While the mutant particles failed to incorporate the authentic HIV-1 Env protein complex, they retained the ability to efficiently and functionally incorporate the amphotropic murine leukemia virus Env protein complex, which has a short cytoplasmic tail. Moreover, incorporation of the autologous Env protein complex could be restored by a second-site mutation that resulted in the truncation of the cytoplasmic tail of the HIV-1 transmembrane glycoprotein. Remarkably, the second-site mutation also restored the ability of MA mutants to replicate in MT-4 cells. These results imply that the long cytoplasmic tail of the transmembrane glycoprotein is responsible for the exclusion of the HIV-1 Env protein complex from MA mutant particles.

Cytoplasm↗