Human actin genes are single copy for alpha-skeletal and alpha-cardiac actin but multicopy for beta- and gamma-cytoskeletal genes: 3' untranslated regions are isotype specific but are conserved in evolution

Retinoic acid inhibits human thyroid peroxidase and thyroglobulin gene expression in cultured human thyrocytes

The effect of retinoic acid (RA) on thyroid peroxidase (TPO) and thyroglobulin (Tg) gene expression was investigated in cultured human thyrocytes. Thyrocytes dispersed from Graves' thyroid tissues were incubated with TSH 5mU/ml and RA 0, 0.01, 0.1, 1.0 microM for 72 h respectively. The samples were then subjected to Northern gel analysis. Northern gel analysis using the specific cDNA probes showed that RA suppressed the accumulation of TPO and Tg mRNA stimulated by TSH in a time- and dose-responsive manner. Furthermore, RA inhibited forskolin and 8-Bromo-cyclic-AMP-induced TPO and Tg gene expression, suggesting a distal action site for these cAMP mediated gene expressions. Immunoprecipitation analysis using the specific monoclonal antibodies showed that TSH increased newly synthesized 100, 75, 36-kDa [35S] TPO. The increased de novo TPO was markedly inhibited by RA. Tg secretion from monolayer cultures was measured by radioimmunoassay. RA also inhibited TSH-induced Tg secretion in a dose dependent manner. RA did not affect [3H] thymidine uptake into primary cultured human thyrocytes. In conclusion, RA inhibits the synthesis of TPO and Tg via the suppression of thyroid-specific gene expression although the exact site of RA action on these genes in human thyroids remains to be further elucidated. These results suggest that RA may play a regulatory role in Tg and TPO gene expression, subsequently resulting in the suppression of thyroid hormone synthesis.

Re-localization of Actsk-1 to mouse chromosome 8, a new region of homology with human chromosome 1

We present here the genetic mapping of the alpha-skeletal actin locus (Actsk-1) on mouse Chromosome (Chr) 8, on the basis of the PCR analysis of a microsatellite in an interspecific backcross. Linkage and genetic distances were established for four loci by analysis of 192 (or 222) meiotic events and indicated the following gene order: (centromere)-Es-1-11.7 cM-Tat-8.3 cM-Actsk-1-0.5 cM-Aprt. Mapping of ACTSK to human Chr 1 and of TAT and APRT to human Chr 16 demonstrates the existence of a new short region of homology between mouse Chr 8 and human Chr 1. Intermingling on this scale between human and mouse chromosomal homologies that occurred during evolution creates disorders in comparative linkage studies.

The use of reverse transcriptase-polymerase chain reaction (RT-PCR) to investigate specific gene expression in multidrug-resistant cells

Expression of specific genes at the level of mRNA can be studied using techniques such as Northern blot, slot/dot blot, RNase protection assay, in situ hybridisation and RT-PCR. In this article these methods of analysis are compared; RT-PCR offers higher levels of specificity and sensitivity than traditional methods of RNA analysis and as such has become the method of choice for the study of gene expression. The RT-PCR technique is described in detail with sections dealing with RNA extraction, choice of primers (including the use of cDNA sequence data bases), PCR and RT-PCR protocols in addition to the limitations of the method. The study of one particular mRNA transcript (MDR1) using RT-PCR is discussed in detail. Recently described methods for quantitation of PCR products are discussed. Quantitative PCR would appear to offer a method of studying gene expression in a more extensive way than has been possible to date.

Anthracyclines selectively decrease alpha cardiac actin mRNA abundance in the rat heart

Anthracyclines are widely used antineoplastic agents, but possess a major side effect of congestive cardiomyopathy. Previously we showed a selective effect of the most commonly used anthracycline, doxorubicin, on decreasing alpha-cardiac (alpha c) actin mRNA abundance in the rat heart. The current studies examined the effects of several anthracyclines (doxorubicin, daunorubicin, and epirubicin) to determine if doxorubicin's previously reported effect on alpha c actin mRNA abundance is: 1) a property shared by other cardiotoxic anthracyclines; 2) selective when compared with a wider spectrum of contractile protein and muscle-specific mRNAs; and 3) related to the characteristic ultrastructural alterations, such as loss of myofilaments, seen in anthracycline-induced cardiomyopathy. Results showed a major selective effect of doxorubicin, daunorubicin, and epirubicin on decreasing alpha c actin mRNA abundance when compared with other contractile protein and muscle-specific mRNAs. In addition, ultrastructural examination of myocardium showed contractile alterations, including loss of myofilaments. These results suggest that decreased expression of selected cardiac genes may relate to the molecular mechanism of clinical anthracycline-induced cardiomyopathy.

Decreased low-density lipoprotein receptor function and mRNA levels in lymphocytes from uremic patients

The mechanisms by which renal failure causes hyperlipoproteinemia remain unclear. To investigate the potential role of the low-density lipoprotein (LDL) receptor in lipoprotein metabolism in uremia we measured LDL receptor function in peripheral blood mononuclear cells (PBMC) from uremic patients and control subjects using a functional assay in which proliferation of lectin-stimulated PBMC in the presence of lovastatin was dependent upon internalization of exogenous cholesterol via a functional LDL receptor. The amount of LDL required to reverse 50% of lovastatin-induced inhibition of proliferation in PBMC from uremic patients was significantly greater (3.6 +/- 1.8 micrograms/ml, N = 33, P < 0.05) than controls, (1.99 +/- 0.6 micrograms/ml, N = 37). Abnormal LDL receptor function in four uremic patients normalized following renal transplantation. To investigate the molecular basis for LDL receptor dysfunction, we directly quantitated LDL receptor messenger RNA (mRNA) in PBMC from uremic patients and control subjects using a ribonuclease protection assay. LDL receptor mRNA expression in uremic patients was 0.42 +/- 0.08 (N = 10), significantly lower (P < 0.015) than in normal subjects, 0.71 +/- 0.08 (N = 14). These data suggest that an acquired defect in LDL receptor function in PBMC from uremic patients exists which may be due to decreased LDL receptor expression. These abnormalities, if present in other tissues, could contribute to the aberrant lipoprotein metabolism which is a consistent feature of uremia.

Centractin is an actin homologue associated with the centrosome

Actin is one of the most ubiquitous, abundant and well-conserved proteins of eukaryotes, participating in many crucial cellular processes including the maintenance of cell shape, motility and cell division. Actins from the most divergent sources still share amino-acid identities in excess of 70% (ref. 3). This may well explain why low-abundance homologues of actin have been difficult to isolate. Genes encoding distant relatives of actin in budding and fisson yeast have now been cloned. We report here the discovery of a vertebrate actin-like protein, which we name centractin. A full-length complementary DNA clone was isolated whose sequence reveals amino-acid identities with actin of over 50%, increasing to more than 70% when conservative amino-acid changes are considered. Northern analysis and western blotting indicate a ubiquitous tissue and species distribution. Morphological and biochemical criteria show that centractin is associated with centrosomes.

Stromal expression of 72 kda type IV collagenase (MMP-2) and TIMP-2 mRNAs in colorectal neoplasia

We undertook an in situ hybridization study to localize the mRNAs for the 72 kda type IV collagenase (MMP-2) and its specific inhibitor (TIMP-2) in 12 colorectal carcinomas, 3 adenomas, and 4 uninvolved resection margins to see how their distributions correlated with that of the reported distribution of MMP-2 protein. Labeling for MMP-2 and TIMP-2 mRNAs was detectable in 10 of 12 carcinomas and in 2 of 3 adenomas. Unexpectedly, we found much stronger signals for MMP-2 and TIMP-2 mRNAs within the mesenchymal cells in the desmoplastic stroma, of endothelial and/or (myo)fibroblastic nature, rather than in tumor epithelial cells in which localization of MMP-2 was anticipated. Our data indicate that stromal cells may have the ability to synthesize a metalloproteinase that degrades basement membrane, and may together with the neoplastic epithelial cells participate actively in the tissue remodeling and disruption of the basement membrane integrity which is characteristic of invasive tumors.

Characterization and chromosomal mapping of the gene encoding the cellular DNA binding protein ILF

Recently we isolated a cellular DNA binding protein, designated interleukin enhancer binding factor (ILF), that binds to purine-rich regulatory motifs in both the HIV-1 LTR and the IL2 promoter. Further analysis of the ILF gene reveals the existence of two mRNA species, both of which encode proteins containing the recently described fork head DNA binding domain. Gel retardation analysis demonstrates that the portion of the ILF protein with homology to the fork head domain is sufficient to mediate DNA binding to a number of related purine-rich sequences. ILF mRNA is expressed constitutively in both lymphoid and nonlymphoid tissues. Chromosomal mapping localizes the ILF gene to human chromosome 17q25, which is a site of chromosomal translocations in some cases of human acute myelogous leukemias. These studies further characterize the structure of the cellular DNA binding protein ILF and may prove valuable in the molecular analysis of possible translocations affecting this gene.

Mechanism of multidrug resistance in human tumour cell lines and complete reversion of cellular resistance

The biochemical basis of the multidrug-resistant (MDR) phenotype has been investigated in drug-resistant sublines derived from LoVo and SW984 human colon carcinoma cell lines by doxorubicin selection. Besides drug extrusion through the plasma membrane, two further observations, both ascribable to the drug transport property of the gp170 glycoprotein, were made. First drug deposition into cytoplasmic membranous structures which allows cells to tolerate a high intracellular drug concentration since it prevents drugs from reaching their cellular target site(s). Secondly drug removal from the complexes formed by interaction of drug with target cellular macromolecules, a phenomenon which extends its an effect that continues after treatment and appears to be the most important resistance mechanism in MDR cells. Treatments based on the gp170 inhibitory property of verapamil were developed that allowed abrogation of resistance in MDR cell lines, a strategy that may be applicable to therapy treatments.

The epidermal growth factor receptor in human pancreatic cancer

The epidermal growth factor receptor (EGFR) and its ligands are thought to be important in the control of proliferation of many epithelial systems, including the exocrine pancreas. Abnormalities in expression of two of the known ligands of the EGFR, transforming growth factor alpha and epidermal growth factor, occur frequently in ductal adenocarcinoma of the human pancreas. We have examined an archival series of cases of pancreatic pathology for expression of the EGFR using the anti-EGFR antiserum 12E and found that there is almost ubiquitous overexpression of EGFR in pancreatic cancer and in chronic pancreatitis. Southern blot analysis showed no evidence of amplification or rearrangement of the EGFR gene. We conclude that an autocrine loop involving the EGFR system may be involved in the genesis of both neoplasia and reactive hyperplasia of pancreatic ductal epithelium.

Expression of glutathione-S-transferase-pi in human tumours

Expression of glutathione-S-transferase-pi (GST-pi) gene was quantitatively analysed on various human tumours (renal cell, colorectal, head and neck, ovarian carcinomas, soft tissue sarcomas; non-Hodgkin lymphomas) and on the corresponding normal tissues when available (kidney, colorectum and head and neck). GST-pi mRNA expression level was found to be significantly higher in tumours (P less than 0.01) than in the normal counterparts (mainly 7.3, 3.5- and 3.0-fold in colorectal, head and neck, and renal carcinomas, respectively). Most tumours displayed a significant relationship between higher GST-pi expression level and poor differentiation grade of tumour cells, thus suggesting a relationship between GST-pi activity, neoplastic transformation and cellular differentiation grade. The high requirement of GST-pi activity neoplastic cells displayed was not singularly related to cellular replication rate. Finally, GST-pi gene expression levels were not affected by chemotherapeutic treatments.

Expression of MDR1 and GST-pi in human soft tissue sarcomas: relation to drug resistance and biological aggressiveness

Human soft tissue sarcomas (HSTS) in adults are a family of mesenchymal tumors characterized by high biological aggressiveness and general refractoriness to chemotherapy. A series of 36 HSTS, 24 untreated and 12 homogeneously treated with a presurgical chemotherapeutic regimen consisting of doxorubicin (intra-arterial) and iphosphamide (intra-vein), was analyzed for expression of MDR1 and the glutathione-S-transferase-pi (GST-pi) gene in order to identify molecular phenomena which may be implicated in the chemoresistance displayed by these tumors. The MDR1 gene was expressed in a greater percentage of drug-treated tumors and at higher levels than in untreated ones. By contrast, chemotherapeutic treatment has no effect on GST-pi mRNA expression. The GST-pi expression level (EL) was much higher in the HSTS with biologically aggressive features. In fact, significant correlations were observed between GST-pi and histologic grade (p = 0.01); aneuploidy (p less than 0.01); and histone H3 EL (p = 0.01), suggesting a possible causal relationship between GST-pi activity and biological aggressiveness in HSTS.

Expression of the mdr1 gene in human colorectal carcinomas: relationship with multidrug resistance inferred from analysis of human colorectal carcinoma cell lines

To investigate whether mdr1 gene products are involved in conferring the chemoresistant phenotype to human colorectal carcinomas (HCCs), we determined the mdr1 mRNA expression level (mdr1 EL) in surgical specimens from 29 pharmacologically untreated patients and analyzed the relationship between mdr1 EL and drug resistance in an in vitro experimental model. This consisted of 7 HCC cell lines chosen to cover the range of mdr1 ELs detected in the neoplastic specimens. No relationship was observed between the mdr1 EL of the HCC cell lines and the degree of chemosensitivity found for each drug tested, regardless of whether mdr1 gene products may [doxorubicin (DOX), vincristine (VCR), and actinomycin-D (ACT-D)] or may not affect [cis-diamminedichloroplatinum (CDDP)] drug-transmembrane equilibria. Conversely, a direct relationship was found between the mdr1 EL of HCC cell lines and the number of drug-resistant (DR) colonies arising from each parent cell line treated in continuous culture with high DOX concentrations. In addition, the chemoresistance index and mdr1 EL of the DR cell variants were roughly proportional to the mdr1 EL of the parent cell line. Our findings suggest that primary HCCs derive multidrug resistance from biochemical mechanism(s) other than mdr1 gene products. However, the mdr1 EL might be indicative of a predisposition to develop DR cell variants after chemotherapeutic treatment.

Retrotransposons and the evolution of mammalian gene expression

Transposable elements, and retroviral-like elements in particular, are a rich potential source of genetic variation within a host's genome. Many mutations of endogenous genes in phylogenetically diverse organisms are due to insertion of elements that affect gene expression by altering the normal pattern of regulation. While few such associations are known to have been maintained over time, two recently elucidated examples suggest transposable elements may have a significant impact in evolution of gene expression. The first example, concerning the mouse sex-limited protein (Slp), clearly establishes that ancient retroviral enhancer sequences now confer hormonal dependence on the adjacent gene. The second example shows that within the human amylase gene family, salivary specific expression has arisen due to inserted sequences, deriving perhaps from a conjunction of two retrotransposable elements.

Adult T-cell leukemia: structures and expression of the p53 gene

Experiments were undertaken to investigate a genetic event involved in leukemogenesis in adult T-cell leukemia (ATL). For this purpose, the p53 gene was chosen for study, since alteration of the gene has been found in a wide variety of human cancers. Structures and expression of the p53 gene in ATL cells were investigated by Southern and Northern blot analyses and a polymerase-chain-reaction single-strand conformation-polymorphism (PCR-SSCP) analysis. Either subtle alterations of the p53 gene or the absence of detectable level of p53 mRNA were found in 2 of 3 acute ATL cell lines and 2 of 12 acute ATL fresh samples. In contrast, no mutation was detected in 4 cases with less aggressive types of ATL (3 chronic and 1 smoldering ATL cases). Mutations found in acute ATL cells occurred in regions highly conserved in evolution and all the cells carrying p53 mutation showed loss of the other p53 allele. These results suggests that alteration of the p53 gene may contribute to progression of the disease in some cases of ATL.

Membrane depolarization by isotonic or hypertonic KCl: differential effects on mRNA levels of tyrosine hydroxylase and dopamine beta-hydroxylase mRNA in PC12 cells

Membrane depolarization is an important and common manipulation used to study the result of enhanced neuronal activity on adaptive changes, including alterations in gene expression. In this study, the effect of elevated KCl, under isotonic and hypertonic conditions, on the changes in mRNA levels of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) was compared. Treatment of PC12 pheochromocytoma cells for several hours with 50 mM KCl, under conditions where osmolarity was maintained, induced TH mRNA levels several fold, without changing DBH mRNA levels (Kilbourne and Sabban, 1990). In contrast, 50 mM KCl added to culture media without adjusting the osmolarity did not alter TH mRNA levels for up to 24 h. Longer continuous exposure to this hypertonic depolarization condition reduced TH mRNA levels to about 10% of control levels. DBH mRNA levels also declined when PC12 cells were treated from 12 h to 5 days with hypertonic 50 mM KCl. The effect appeared to be specific, since actin mRNA levels were elevated about 2-fold with these same hypertonic treatments. As a control for osmotic changes, 50 mM NaCl was used and did not alter TH or DBH mRNA levels. Viability of the cells was maintained and total protein synthesis was reduced somewhat after 12 h of exposure to hypertonic 50 mM KCl, and remained relatively constant for as long as 4 days. Thus, there appears to be an interaction between osmolarity and elevated KCl since very different results of the effects of membrane depolarization on the mRNA levels for the catecholamine biosynthetic enzymes were obtained depending on the osmolarity of the cultures. The extent of elevation of TH mRNA with isotonic KCl was also dependent on cell density. At high cell densities, membrane depolarization no longer induced TH mRNA levels. The results of this study indicate the experimental parameters which can be crucial in studies of membrane depolarization.

The serum concentrations of the aminoterminal propeptide of procollagen type III and the hepatic content of mRNA for the alpha 1 chain of procollagen type III in carbon tetrachloride-induced rat liver fibrogenesis

Serum concentrations of the aminoterminal propeptide of procollagen type III (PIIIP) are elevated in fibrogenic diseases of the liver, but the mechanism of elevation is not fully understood. To investigate the mechanism, we compared serum concentrations of PIIIP with total liver content of mRNA for the pro alpha 1 (III) chain, in rats with carbon tetrachloride (CCl4)-induced liver fibrosis. Adult male rats received CCl4 in mineral oil twice weekly for 8 weeks and were compared with age-matched controls. Serum concentrations of PIIIP were measured by a specific radioimmunoassay; molecular sizes of PIIIP in serum were also determined. Pro alpha 1 (III) mRNA content in the liver was quantitated by RNA slot-blot hybridization and chemical measurement of total hepatic RNA content. Total collagen content of the liver was estimated by hydroxyproline measurement. All CCl4-treated animals had septal fibrosis after 4 weeks, and evidence of cirrhosis (regenerative nodules, ascites) was seen after 7 weeks of treatment. Serum concentrations of PIIIP and pro alpha 1 (III) mRNA content in the liver were correlated well until cirrhosis has established. They increased simultaneously after 3 weeks of treatment, 1 week before any elevation of hepatic hydroxyproline could be detected. After cirrhosis has established, pro alpha 1 (III) mRNA content in the liver decreased markedly, but serum PIIIP levels continued to be elevated. Hepatic hydroxyproline plateaued after 5 weeks. The molecular sizes of serum PIIIP indicate the release of intact native procollagen peptide during the development of cirrhosis. In conclusion, at least in CCl4-induced liver fibrosis in the rats, serum PIIIP levels can be used as a fibrogenic marker for the period progressing to cirrhosis. But the use of the serum PIIIP levels in cirrhosis seems to be limited by factors other than liver fibrogenesis.

Anchorage-independent growth and the expression of cellular proto-oncogenes in normal human epidermal keratinocytes and in human squamous cell carcinoma cell lines

The expression of multiple cellular proto-oncogenes and the in vitro anchorage-independent growth of normal human epidermal keratinocytes and several human squamous cell carcinoma cell lines were studied and correlated. Squamous cell carcinoma cell lines KB, Si Ha, HEp-2, and Fa Du showed high anchorage independency, and MS 751 and A-253 cell lines had minimum independency. However, the normal keratinocytes and the A-431 cell line did not show anchorage-independent growth. Both the normal human epidermal keratinocytes and cancer cell lines expressed multiple proto-oncogenes such as src, erb B-1, abl, fos, raf, H-ras, and myc, and the amount of expression of these oncogenes was notably higher in the cancer cell lines than in the normal keratinocytes. The expression of proto-oncogenes from the monolayer cultures of the cancer cell lines is poorly correlated with the anchorage independency of the cells. These data indicate that the anchorage independency is not directly linked to the expression of specific cellular proto-oncogene(s) of the monolayer cancer cell cultures.

Expression of hematopoietic growth factor RNAs in human mesenchymal cells from various organs

Experiments were undertaken to study expression of hematopoietic growth factor RNAs in mesenchymal cells from a variety of organs including bone marrow, foreskin, gingiva, and lung. Cells from each organ had negligible expression of RNAs coding for granulocyte (G), macrophage (M), and granulocyte-macrophage (GM) colony stimulating factor (CSF), interleukin 1 beta (IL-1 beta), and IL-6. Fibroblasts from each tissue had a comparable ability to express the same cytokine RNAs. Surprisingly, the stimuli for expression of G-CSF RNA was disparate from the stimuli for expression of the other cytokine RNAs. While IL-1 beta enhanced accumulation of G-CSF RNA, tumor necrosis factor alpha (TNF) and 12-O-tetradecanoylphorbol-13-acetate (TPA) did not. In contrast, IL-1 beta, TNF, and TPA equally stimulated increased levels of M-CSF, GM-CSF, IL-1 beta and IL-6 RNAs.

D-factor: modulation of expression in fibroblasts

Differentiation inducing factor (D-factor) is a recently described protein. The gene has been cloned, but little is known concerning regulation of expression of the gene. Our study showed that fibroblasts from a variety of tissues (lung, bone marrow, gingiva, foreskin) constitutively expressed D-factor RNA. Levels of expression of this gene increased in fibroblasts of each of the tissues after exposure to several stimuli including products of activated macrophages and lymphocytes (tumor necrosis factor (TNF), interleukin 1 and lymphotoxin). Other stimuli were those capable of activating either protein kinase C (12-O-tetradecanoylphorbol-13-acetate (TPA) and teleocidin), G-binding proteins (NaF) or those inhibiting protein synthesis (cycloheximide). Accumulation of D-factor RNA by TNF may in part be explained by stabilization of D-factor transcripts; TPA and cycloheximide clearly stabilized D-factor transcripts. We and others have shown that these same signals similarly stimulated fibroblasts to express RNAs coding for a variety of cytokines including three colony-stimulating factors as well as interleukins 1 and 6. Taken together, D-factor probably is a participant in the cascade of cytokines that are produced in mesenchymal cells after various stimuli such as bacterial invasion.

Identification and partial characterization of genes that are transactivated by different pathways in quiescent mouse cells stimulated with serum

We have identified four cDNA clones, cl-1, cl-5, cl-15, and cl-16, that represent genes induced by serum in resting mouse 3T3 cells. Partial sequence analysis of the four cDNAs indicated that cl-15 corresponds to the mouse beta-actin gene. Comparison of the DNA sequences of the other three clones with the sequence data bank (Genbank) showed little homology to other known DNA sequences and thus represent novel genes. The level of the mRNAs corresponding to the four genes began to increase in resting cells following serum stimulation, reached a peak between 5 h and 8 h and then started to decline. Inhibitors of transcription diminished the induction of the mRNAs corresponding to the four genes. Cycloheximide and anisomycin had little effect on the induction of beta actin mRNA while the induction of the other three genes was suppressed by the same inhibitors. 12-O-Tetradecanoylphorbol-13-acetate and the calcium ionophore A23187 enhanced the expression of the cl-16 mRNA while epidermal growth factor, fibroblast growth factor, or insulin enhanced the expression of cl-1- and cl-5-specific transcripts. The level of beta-actin mRNA was elevated in resting cells by epidermal growth factor and 12-O-tetradecanoylphorbol-13-acetate and to a lesser extent by fibroblast growth factor, insulin, and dibutyryl cyclic AMP-elevating agents. Pertussis toxin, an inhibitor of the action of G proteins, did not significantly suppress the activation of the four genes by serum. However, 2-aminopurine, a protein kinase inhibitor, suppressed the induction of the four transcripts in serum-stimulated cells. The possible pathways involved in the activation of these genes in resting cells are discussed.

Newly identified type of beta actin reduces invasiveness of mouse B16-melanoma

Low metastatic parent B16 melanoma and isolated B16-F1 cell lines have a third actin designated as beta m(Ax:previously). beta m actin is scantily or not at all detected in highly metastatic cell lines, such as B16-F10 and BL6. To directly assess the physiological role of beta m in phenotypic changes of B16 melanoma, we transfected expression plasmids of beta m into B16-F10 cells. The actin expressed in the transfectants is located largely in cytoskeletal fractions. The transfectants exhibited a larger number of stress fibers and a lower invasiveness than did the recipient cells. Thus, beta m actin plays an important role in the organization of actin stress fibers, the result being a decrease in invasiveness of B16 melanoma.

Lipopolysaccharide from Actinobacillus actinomycetemcomitans stimulates macrophages to produce interleukin-1 and tumor necrosis factor mRNA and protein

Actinobacillus actinomycetemcomitans is associated with periodontal disease in children and adults. We report that low concentrations of lipopolysaccharide (LPS) from A. actinomycetemcomitans stimulated human macrophages to increase dramatically their accumulation of mRNA coding for interleukin-1 alpha (IL-1 alpha), IL-1 beta as well as tumor necrosis factor (TNF). Protein levels of IL-1 and TNF alpha also increased. Levels of these mRNAs increased by 4-5 fold as compared with unstimulated macrophages when these cells were cultured with as little as 2 ng/ml LPS from A. actinomycetemcomitans. Polymyxin binds and blocks the action of LPS; polymyxin inhibited the ability of LPS from A. actinomycetemcomitans to increase levels of IL-1 beta mRNA. The LPS of A. actinomycetemcomitans stimulated increased levels of IL-1 beta mRNA in the presence of cycloheximide, showing that stimulation by this LPS did not require new synthesis of protein. Furthermore, dexamethasone inhibited the ability of LPS from A. actinomycetemcomitans to stimulate the accumulation of mRNA coding for IL-1 beta. A. actinomycetemcomitans is an invasive microorganism of the gingiva; high intragingival numbers correlate with sites undergoing local destruction of the periodontium. IL-1 alpha, IL-1 beta, and TNF are potent monokines that mediate inflammation and resorption of bone. Out studies suggest that macrophages migrating to these gingival sites of A. actinomycetemcomitans infection will be stimulated by LPS of A. actinomycetemcomitans to produce IL-1 alpha, IL-1 beta and TNF. These cytokines will mediate gingival inflammation and stimulate resorption of alveolar bone.

Sequential activation of HOX2 homeobox genes by retinoic acid in human embryonal carcinoma cells

RETINOIC acid had been implicated as a natural morphogen in chicken and frog embryogenesis, and is presumed to act through the gene regulatory activity of a family of nuclear receptors. Homeobox genes, which specify positional information in Drosophila and possibly in vertebrate embryogenesis, are among the candidate responsive genes. We previously reported that retinoic acid specifically induces human homeobox gene (HOX) expression in the embryonal carcinoma cell line NT2/D1. We now show that the nine genes of the HOX2 cluster are differentially activated in NT2/D1 cells exposed to retinoic acid concentrations ranging from 10(-8) to 10(-5) M. Genes located in the 3' half of the cluster are induced at peak levels by 10(-8) M retinoic acid, whereas a concentration of 10(-6) to 10(-5) M is required to fully activate 5' genes. At both high and low retinoic acid concentrations, HOX2 genes are sequentially activated in embryonal carcinoma cells in the 3' to 5' direction.

Independent gene evolution in the potato actin gene family demonstrated by phylogenetic procedures for resolving gene conversions and the phylogeny of angiosperm actin genes

Nine different actin DNA sequences were isolated from the common potato, Solanum tuberosum, and the nucleotide sequence of five actin loci and of two allelic variants are presented. Unlike the wide variation in intron position among animal actin genes, the potato actin genes have three introns situated in the same positions as reported for all other angiosperm actin genes. Using a novel combination of analytical procedures (G-test and compatibility analysis), we could not find evidence of frequent large or small nonreciprocal exchanges of genetic material between the sequenced loci, although there were a few candidates. Resolution of such gene conversion events and the quantification of independence of gene evolution in multigene families is critical to the inference of phylogenetic relationships. Comparison with actin genes in other angiosperm species suggests that the actin multigene family can be divided into a number of subfamilies, evolved by descent rather than gene conversion, which are of possible functional origin, with one major subfamily diversification occurring before the divergence of monocots and dicots. The silent rate of nucleotide substitution was estimated to be similar to that suggested for a number of other plant nuclear genes, whereas the replacement rate was extremely slow, suggestive of selective constraints.

The amount of the endogenous and exogenous skeletal muscle actin mRNA in the heart of transgenic mice is affected by the genotype of the cardiac actin gene

Both skeletal muscle and cardiac actins are co-expressed in the newborn heart. However, the amount of the skeletal muscle actin and its mRNA rapidly decreases during early development and the cardiac actin predominates in the adult heart. In BALB/c and DBA mice there is a mutation in the cardiac actin gene which is associated with decreased levels of cardiac actin mRNA and high levels of the skeletal muscle actin transcript in the adult heart. To examine the possibility that the amount of cardiac actin gene product modulates the expression of the skeletal muscle actin gene in the heart, transgenic mice carrying a tagged skeletal muscle actin gene were produced, and the expression of the endogenous and endogenous and exogenous actin gene was analyzed in offspring carrying different combinations of the cardiac actin alleles. It was found that both the endogenous and exogenous skeletal muscle actin genes were expressed at low levels in the heart of adult mice homozygous for the wild-type cardiac actin gene allele, at abnormally high levels in mice homozygous for the mutated cardiac actin allele, and at intermediate levels in heterozygous mice. This shows that the level of expression of the cardiac actin gene has a trans effect on the expression of the skeletal muscle actin gene.

Quantitative changes in cytoskeletal beta- and gamma-actin mRNAs and apparent absence of sarcomeric actin gene transcripts in early mouse embryos

Actin is known to be synthesized both during oogenesis and in cleavage-stage embryos in mice. Cytoskeletal beta-actin appears to be the major component, followed by gamma-actin, but the synthesis of alpha-actin has also been inferred from protein electrophoretic patterns. We have studied the expression of cytoskeletal (beta- and gamma-) and sarcomeric (alpha-cardiac and alpha-skeletal) actin genes at the level of the individual mRNAs in blot hybridization experiments using isoform-specific RNA probes. The results show that there are about 2 x 10(4) beta-actin mRNA molecules in the fully grown oocyte; this number drops to about one-half in the egg and less than one-tenth in the late two-cell embryo but increases rapidly during cleavage to about 3 x 10(5) molecules in the late blastocyst. The amount of gamma-actin mRNA is similar to that of beta-actin in oocytes and eggs but only about 40% as much in late blastocysts, indicating a differential accumulation of these mRNAs during cleavage. The developmental pattern of beta- and gamma-actin mRNA provides a striking example of the transition from maternal to embryonic control that occurs at the two-cell stage and involves the elimination of most or all of the maternal actin mRNA. There was no detectable alpha-cardiac or alpha-skeletal mRNA (i.e., less than 1,000 molecules per embryo) at any stage from oocyte to late blastocyst, suggesting that the sarcomeric actin genes are silent during preimplantation development.

Establishment and characterization of a leukemic murine cell line derived from MCF 247 MuLV-induced T-cell lymphoma

Understanding of the leukemic evolution of human non-Hodgkin's lymphomas is hindered by the lack of appropriate animal models. For this purpose, a highly leukemic cell line NQ22, derived from a MCF 247 murine leukemia virus (MuLV)-induced murine T-cell lymphoma, was established, and its preliminary characterization is described. The NQ22 cell line is easily transplantable subcutaneously (s.c.) into syngeneic AKR mice exhibiting early peripheral blood invasion and widespread dissemination with a leukemic pattern of infiltration. Such peculiar in vivo behavior is a stable phenotypic feature, probably determined genetically. Biological and differentiation characteristics of the NQ22 cell line were analyzed and compared to those of other non-leukemic T-lymphoma lines. In addition, no evidence of possible involvement of plasminogen activator (PA) enzymes and of their inhibitors (PAI) in the spreading ability of NQ22 cells was observed.

The mouse smooth muscle gamma actin gene is on chromosome 6

Smooth muscle gamma actin (Actg) is expressed in smooth muscle and in haploid male germ cells. In order to further characterize the Actg gene, a 60-nucleotide-long isotype-specific probe was synthesized. Single bands of DNA were detected when this oligonucleotide was used to probe blots of mouse genomic DNA digested with PstI, EcoRI, KpnI, or XbaI. These results suggest Actg is a single-copy gene with no detectable pseudogenes. The Actg gene was mapped to mouse chromosome 6 by Southern blot analysis of DNA isolated from 15 mouse-hamster hybrid cell lines.

c-myc overexpression is a tumor-specific phenomenon in a subset of human colorectal carcinomas

The transcriptional activity of the c-myc proto-oncogene was examined in 25 primary human colorectal carcinomas and their corresponding normal mucosae. The purpose was to determine whether the elevated levels of c-myc expression, frequently detected in this type of tumor, might be the consequence of alterations in the cell growth rate or the effect of a real transcriptional deregulation of the gene. In about 44% of the tumors the elevated c-myc expression was consequent to the enhanced growth rate of the neoplastic tissue, as estimated by the expression of the S-phase-specific histone H3 gene. In the other 56%, c-myc overexpression did not entirely depend on the proliferative activity of the neoplastic population. In this latter group, c-myc deregulation did not reside in structural modifications of the putative regulatory regions of the gene. Therefore, c-myc overexpression, at least in a subset of colorectal cancer, seems to be consequent to alterations in transregulative phenomena exerted on the c-myc gene by other genetic loci.

Adenovirus early region 3 promoter regulation by E1A/E1B is independent of alterations in DNA binding and gene activation of CREB/ATF and AP1

Transcription of the adenovirus early region 3 promoter is strongly induced by the adenovirus E1A protein. Previous DNase I footprinting has indicated that four regions in this promoter serve as binding sites for HeLa nuclear proteins. These include binding sites for NF-1 (site IV), AP1 (site III), CREB/activating transcription factor (ATF) (site II), and TATA (site I). To determine the relative importance of these sites in both the in vivo and in vitro transcriptional regulation of the E3 promoter, oligonucleotide-directed mutagenesis of these sites was performed. Each of these constructs was assayed by transfection onto HeLa cells in the presence of either dl434, an E1A/E1B deletion mutant, or wild-type adenovirus. Mutations of either the ATF- or AP1-binding sites but not the TATA- and NF1-binding sites resulted in severe decreases in both basal and E1A/E1B-induced transcriptional levels. These constructs were also assayed in in vitro transcription assays with cellular extracts prepared from dl434-infected or wild-type-adenovirus-infected HeLa cells. The wild-type E3 promoter was transcribed approximately 30 times more efficiently in extracts containing the E1A/E1B proteins compared with extracts lacking these proteins. Mutations of either the TATA element, the ATF site, or the AP1-binding site decreased both basal and E1A/E1B-induced transcriptional levels. Gel retardation analysis using these extracts indicated that the binding to ATF, AP1, or NF1 oligonucleotides was not altered in the presence of the E1A/E1B proteins compared with extracts lacking these proteins. Northern (RNA) blot analysis of c-jun and CREB RNA prepared from wild-type adenovirus and dl434-infected cells indicated that the levels of these RNAs were not altered by the E1A/E1B proteins. Immunoprecipitation of AP1 and CREB from both dl434- and wild-type-adenovirus-infected cells indicated that the amounts of these proteins were not significantly altered. These results suggest that E1A/E1B-induced activation of the E3 promoter does not involve activation of transcription factor genes nor a change in the DNA binding activity of important promoter-binding components. Our results are consistent with a model in which the E1A/E1B proteins either directly or indirectly alter the interactions of factors that bind to the basal E3 promoter transcription complex, thereby inducing transcription.

A micromethod for the isolation of total RNA from adipose tissue

We have developed a simple and rapid procedure for the isolation of total RNA from small amounts of adipose tissue. Using this method, it is possible to obtain quantitative recovery of RNA from less than 300 mg of adipose tissue, with an average yield of 70 micrograms of RNA per gram of adipose tissue. Northern blot analysis of rat epididymal adipose tissue RNA samples was performed using a beta-actin probe and demonstrated that intact total RNA had been isolated. The procedure has been adapted for use in 1.5-ml microcentrifuge Eppendorf tubes, providing a convenient and inexpensive method for the reproducible recovery of intact RNA from sparse samples of adipose tissue.

Collagen and elastin metabolism in hypertensive pulmonary arteries of rats

We evaluated the processes controlling the accumulation of collagen and elastin in main pulmonary arteries of rats during an episode of hypoxic pulmonary hypertension. Explant cultures of main pulmonary arteries were incubated with [3H]proline to measure collagen and protein synthesis and percent collagen synthesis. Elastin synthesis was measured by [14C]valine incorporation into insoluble elastin. Relative collagen synthesis increased twofold (from 1.1 +/- 0.2 x 10(3) to 2.0 +/- 1.0 x 10(3) disintegrations per minute [14C]hydroxyproline/vessel/hr/mg protein), relative collagen synthesis doubled (from 2% to 4-5% of total protein synthesis), and elastin synthesis increased ninefold (from 0.4 +/- 0.2 x 10(4) to 3.6 +/- 0.6 x 10(4) dpm [14C]valine/vessel/hr/mg protein) in early hypertension. The level of pro alpha l(I) collagen RNA paralleled the relative collagen synthetic rate during the study period. Within 7 days of recovery from hypoxia, collagen and elastin contents were normal. We conclude that collagen and elastin in main pulmonary arteries are synthesized rapidly during an episode of hypoxic pulmonary hypertension and that collagen and elastin are rapidly removed from the hypertensive vessel during normoxic recovery.

Cell differentiation and altered IMP dehydrogenase expression induced in human T-lymphoblastoid leukemia cells by mycophenolic acid and tiazofurin

The IMP dehydrogenase inhibitors mycophenolic acid (MPA) and tiazofurin (TZ) induce a time- and dose-dependent inhibition of cell growth, as well as differentiation in T-lymphoid CEM-2 leukemia cells. The differentiated cells have acquired a suppressor/cytotoxic T-lymphocyte phenotype characterized by reactivity with maturation-specific monoclonal antibodies. Coadministration of guanosine and hypoxanthine reduces the growth inhibition and diminishes the induction of differentiation by either MPA or TZ. No such reduction was observed for differentiation induced by phorbol 12-myristate 13-acetate (PMA), another inducer of a suppressor/cytotoxic phenotype in CEM-2 cells. During the first 2 days of treatment with MPA or TZ, a pattern of stable IMPDH mRNA levels and increased amounts of cellular enzyme was observed, perhaps, because of compensation for the inhibitor-mediated decrease in cellular IMPDH activity or a MPA- or TZ-mediated decrease in proteolysis of IMPDH. PMA treatment decreased the levels of IMPDH mRNA, protein, and activity. In addition, treatment of CEM-2 cells with either IMPDH inhibitors or PMA caused different alterations of the ribonucleotide pools. The lack of a consistent pattern of IMPDH expression in CEM-2 cells treated with IMPDH inhibitors or PMA indicates that no general association exists between the induction of cell differentiation and the expression of IMPDH. Nevertheless, our results indicating that IMPDH inhibitors can induce differentiation in CEM-2 cells suggest that this treatment may provide a useful approach to circumvent the differentiation block in some tumor cells.

Heterogenic mRNAs with an identical protein-coding region of the human embryonic myosin alkali light chain in skeletal muscle cells

The formation of human myotubes in culture is accompanied by the induction of developmentally regulated, muscle-specific genes. We have studied the expression of human myosin light chain proteins and mRNAs during myogenesis in culture, in particular the skeletal embryonic myosin light chain 1 (MC1emb), which is indistinguishable from MLC1 of adult atrial cardiac muscle (MLC1A) as has been shown for rodent and bovine MLC1emb. We have identified distinct MLC1emb/MLC1A mRNAs in cultured human skeletal muscle cells that differ in their 5' and 3' untranslated regions but contain identical protein-coding regions. The alternative 3' untranslated region is detectable also in RNA of human atria. The different MLC1emb RNAs are likely to be encoded by one gene. It appears that the two MLC1emb 5' untranslated regions of the human gene are specific for man. In the mouse, only one 5' untranslated region of the MLC1emb gene has been detected.

Repression of nuclear lamin A and C gene expression in human acute lymphoblastic leukemia and non-Hodgkin's lymphoma cells

The lamins A, B and C which are differentially expressed during ontogenesis and differentiation are karyoskeletal proteins forming a polymeric meshwork at the inner nuclear membrane. Using Northern blot analyses we investigated the steady state levels of the three lamin specific RNA transcripts in neoplastic cells derived from 16 untreated patients with acute lymphoblastic leukemia (ALL) or non-Hodgkin's lymphoma (NHL) and in ALL and NHL established cell lines. Whereas lamin B mRNA was present in all, lamin A and C transcripts were observed in none of the malignant cell samples except one of a common-ALL patient (precursor B-ALL, cytoplasmic mu chain negative). All three lamin mRNAs were detected in normal peripheral blood lymphocytes, however, only after mitogenic stimulation with concanavalin A. Our results provide evidence that expression of lamin A and C is repressed in neoplastic blast cells derived from patients with ALL or NHL and suggest that lamin A and C gene repression is not related to cell proliferation but might be relevant to the differentiated stages of the lymphoid cells in vivo.

Isolation and characterization of beta-actin gene of carp (Cyprinus carpio)

A beta-actin gene of carp (Cyprinus carpio) was isolated from a genomic EMBL3 library. The nucleotide sequence of the gene indicates six exons spanning 3.6 kb. Southern blot hybridization of restriction endonuclease digests of carp genomic DNA indicate that there are two copies of the beta-actin isotype and several other species of actin genes. The transcriptional start site is 85 bp and 24 bp downstream respectively from consensus CCAAT and TATA promoter elements. The organization of the carp beta-actin gene is identical to that of chicken, human, and rat genes in terms of size, exon/intron locations and junctions and in having a translationally silent first exon. The fish gene is 90% and 99% conserved at the nucleotide and amino acid levels, respectively, with land vertebrate beta-actin genes. Northern blot analysis of beta-actin gene expression indicated that the gene is highly expressed in brain, less so in muscle, and much less so in liver cells. The putative beta-actin proximal promoter of carp, identified by the conservation of known actin regulatory sequences, is transcriptionally active in both mammalian and piscine cells.

A coordinated proto-oncogene expression characterizes MCF 247 murine leukemia virus-induced T-cell lymphomas irrespectively of proviral insertion affecting myc loci

Proto-oncogene transcriptional activation was analyzed in a group of MCF 247 MuLv-induced T-cell lymphomas to identify transformation-specific gene activations and determine whether the proviral insertion near a myc gene could promote a peculiar mechanism of transformation through a differential proto-oncogene expression pattern. Of the six lymphomas analyzed, three showed the MCF 247 provirus integrated within the N-myc locus, one carried the provirus integrated near c-myc, whereas for the remaining two, no evidence of proviral integrations in any of the known myc loci was obtained. Independently of the integrative events, the pattern of proto-oncogene expression was almost identical in all six lymphomas. These findings seem to rule out the existence of a peculiar pathway of transformation associated with the proviral insertion near a myc locus. Moreover, the transcription pattern observed was qualitatively identical to that displayed by normal thymocytes; only quantitative differences in c- or N-myc, c-myb and Ha-ras were observed. These results suggest that the T-cell proto-oncogene activation program is not qualitatively affected by the transforming event(s).

Effects of ionizing radiation on expression of genes encoding cytoskeletal elements: kinetics and dose effects

We examined the modulation in expression of genes encoding three cytoskeletal elements (beta-actin, gamma-actin, and alpha-tubulin) in Syrian hamster embryo (SHE) cells following exposure to ionizing radiations. Early-passage SHE cells were irradiated in plateau phase with various low doses (12-200 cGy) of neutrons, gamma-rays, or x-rays. RNA samples were prepared from cells at different times postexposure and were analyzed for levels of specific transcripts by northern blots. The results revealed that alpha-tubulin was induced by both high-linear energy of transfer (LET) (neutrons) and low-LET (gamma-rays and x-rays) radiations with similar kinetics. The peak in alpha-tubulin mRNA accumulation occurred between 1 and 3 h postexposure; for gamma-actin mRNA, accumulation was similarly induced. For both gamma-actin and alpha-tubulin, the higher the dose during the first hour postexposure (up to 200 cGy gamma-rays), the greater the level of mRNA induction. In contrast, mRNA specific for beta-actin showed decreased accumulation during the first hour following radiation exposure, and remained low up to 3 h postexposure. These results document the differential modulation of genes specific for cytoskeletal elements following radiation exposure. In addition, they demonstrate a decrease in the ratio of beta-actin:gamma-actin mRNA within the first 3 h following gamma-ray exposure. These changes in mRNA accumulation are similar to those reported in some transformed cell lines and in cells treated with tumor promoters, which suggests a role for changes in actin- and tubulin-mRNA expression in radiation-mediated transformation.