Biomedical subjects

M L Avantaggiati

Publications and source records attributed to M L Avantaggiati.

28 records · Page 2Linked to original sources

PubMed1993

The hepatitis B virus (HBV) pX transactivates the c-fos promoter through multiple cis-acting elements.

The hepatitis B virus (HBV) X protein (pX) stimulates transcription regulated by cis-acting elements that control many viral and cellular genes, including the c-myc and the c-fos proto-oncogenes. Using several c-fos promoter deletion mutants, we found the serum-responsive element (SRE) located at -315, the modified TPA-responsive element located at -296 (fos-AP-1 binding site, FAP) and the region spanning from nucleotide -220 to -120, which contains an NF1-like site and several stretches of sequence homologous to the AP-2 consensus binding sites, to be responsive to pX. pX does not modify the pattern of the retarded complexes bound to the SRE/FAP region which, in our system, appears to be occupied by SRE-binding factors. The activation of the SRE does not involve complex formation between SRE-binding factors and pX, it is not associated with an increase in serum response factor binding to the SRE and it does not determine changes in SRE mobility-shift pattern.

Animals↗

PubMed1992

The hepatitis B virus X protein transactivation of c-fos and c-myc proto-oncogenes is mediated by multiple transcription factors.

We have constructed two expression vectors in order to study the action of the HBV 17 Kd X protein on the c-fos and c-myc promoters. The results show that the promoters contain multiple elements that respond to X protein, suggesting involvement of multiple transcription factors. The exact mechanism of the interaction remains elusive, but our data allow speculation about the factors that may be influenced.

Chloramphenicol O-Acetyltransferase↗

PubMed1992

Truncated pre-S/S proteins transactivate multiple target sequences.

In order to investigate the transactivational function of HBV truncated preS/S proteins we have constructed two sets of plasmids and have tested their transactivational potential on the c-myc regulatory sequences and the TPA-responsive element. We found that preS/S proteins only become transactivationally active when truncated at the carboxy terminal end. Furthermore, using immunofluorescence microscopy we determined that the proteins are located exclusively in the cytoplasm, apparently ruling out DNA binding and activation of factors in the nucleus.

Chloramphenicol O-Acetyltransferase↗

PubMed1992

Characterization of the hepatitis B virus preS/S region encoded transcriptional transactivator.

A transactivating function generated by carboxy-terminal truncation of the HBV envelope proteins has been recently described. To characterize the preS/S protein domains responsible for transactivation, preS1/S2/S and preS2/S 3' deletion mutants under the control of the adenoviral major late promoter were tested for their transactivating potential in cotransfection experiments using the c-myc and c-fos regulatory sequences as targets. Deletion of the carboxyterminal hydrophobic domain of the S protein and the presence of the endoplasmic reticulum insertion signal I (ER signal I) are required for the generation of the preS/S transactivating function. Multiple transcription factors binding sites (i.e., TRE, SRE, and NFkB sites) mediated the truncated preS/S-induced activation of the target regulatory sequences. The transactivation phenomenon is linked, at least in part, to the protein kinase C signaling pathway.

Cloning, Molecular↗

PubMed1991

Defective and nondefective adenovirus vectors for expressing foreign genes in vitro and in vivo.

We have constructed recombinant adenoviruses (Ad), with functional or defective E1a genes, which harbor either the hepatitis B (HB) virus s gene encoding the HB surface antigen, as well as the pre-S2 epitopes, or the bacterial gene encoding chloramphenicol acetyltransferase (CAT) under control of the Ad major late promoter (MLP). The recombinant viruses defective for E1a (Ad.MLP.S2 and Ad.CAT), which can be efficiently propagated only on 293 cells that complement this defect, and the nondefective (Ad.MLP.S2.E1A) recombinant were used to infect a wide spectrum of cells of different origin. The yields of HBs and CAT proteins obtained with these different recombinant viruses demonstrate no real advantage to using nondefective vectors, whatever the cell type infected. The injection into chimpanzees of Ad.MLP.S2 does not elicit the production of antibodies, but can immunologically prime the animals, resulting in a partial protection against HBV challenge.

Adenoviruses, Human↗

PubMed1991

Full-length and truncated versions of the hepatitis B virus (HBV) X protein (pX) transactivate the cmyc protooncogene at the transcriptional level.

The products of the human hepatitis B virus (HBV) and woodchuck hepatitis B virus X genes (pXs) transactivate homologous and heterologous genes including the HBV-X and core promoters, the human immunodeficiency viruses 1 (HIV-1) and 2 (HIV-2) long terminal repeats and the beta interferon regulatory sequences. We report here that pX is also able to influence the expression of both extrachromosomal transfected c-myc regulatory sequences and endogenous c-myc gene. pX acts by increasing transcription of the c-myc gene and do not affect c-myc mRNAs stability. The presence of the first AUG of the X-ORFs is indeed necessary for the production of an active pX. The very carboxyterminus of the pX protein is dispensable for this transactivating activity and at least one domain important for its action is located between aminoacids 103 and 117.

Adenoviruses, Human↗

PubMed1991

Antibodies to hepatitis C virus in patients with hepatocellular carcinoma.

To study the potential relationship between the hepatitis C virus (HCV), the major etiologic agent of parenterally transmitted non-A, non-B hepatitis, and the development of hepatocellular carcinoma (HCC), we tested the presence of anti-HCV antibodies in sera from a large panel of HCC patients of different racial and geographical origins. Anti-HCV antibodies were detected in 82 out of 114 (71.9%) HBsAg-negative HCC patients and in 15 out of 53 (28.3%) HBsAg-positive patients. No significant difference in the prevalence of anti-HCV antibodies was found in the HBsAg-negative HCC patients when they were divided according to presence of anti-HBs and/or anti-HBc antibodies, or absence of all hepatitis B virus (HBV) serological markers. The prevalence of anti-HCV antibodies was similar in HCC patients of Caucasian and African origin. No differences were noted when the patients were grouped according to sex. The mechanisms by which HCV might contribute to the development of HCC need to be further investigated. As for HBV infection, the necro-inflammation associated with HCV infection may induce cirrhosis, regeneration and eventually malignant transformation. The finding that few anti-HCV patients had HCC which is not superimposed on cirrhosis suggests that HCV could, however, exert some direct effect on the development of HCC.

Adolescent↗

PubMed1991

Hepatitis B virus and hepatocellular carcinoma: a possible role for the viral transactivators.

Several epidemiological studies have demonstrated a link between chronic B virus infection and primary hepatocellular carcinoma (PHC). HBV DNA sequence integrations into the host cell genome have often been observed in hepatocarcinoma tissues. However, since only in a few cases of PHC the target of HBV-DNA insertion has been identified, alternative mechanisms for HBV-induced hepatocyte transformation have been investigated. Like many other DNA viruses, the hepatitis B virus bears a transactivational potential. Both full length and truncated versions of HBV X protein are able to influence the expression of cellular nuclear protooncogenes c-fos and c-myc. A second transcriptional activator is encoded by the PreS/S region of HBV, but its activity on viral and cellular genes become evident only after dislocations from its downstream sequences. Thus, HBV is able to influence infected cell growth and differentiation using both native proteins, newly generated truncated proteins and virus-cell fusion polypeptides.

Carcinoma, Hepatocellular↗

PubMed1990

Hepatitis B virus X protein transactivates the long terminal repeats of human immunodeficiency virus types 1 and 2.

The X gene product of the hepatitis B virus (HBV) has been expressed transiently in HepG2 cells, and the 17-kilodalton protein has been detected by Western (immuno-) blot analysis. Cotransfection of the X gene with the long terminal repeat of human immunodeficiency virus type 1 or 2 results in a stimulation of long terminal repeat-directed expression that is higher than the X-induced stimulation of the HBV enhancer linked to either autologous promoter or to the heterologous simian virus 40 promoter. A frameshift mutation abolished this transactivation. In vitro nuclear transcription assays revealed that HBV X acts at the transcriptional level. The carboxy terminus of the HBV X protein does not seem to be necessary for its transactivating activity, as demonstrated by using HBV X protein deletion mutants.

Blotting, Western↗

PubMedDate not supplied

The molecular basis of myocardial hypertrophy.

Myocardial hypertrophy is an adaptive response of the heart to several pathological situations aimed at maintaining adequate cardiac contractile function. This process is characterized by complex qualitative and quantitative changes of both cardiomyocytes and nonmyocyte cardiac cells. The initial stimulus inducing these cellular responses is parietal stretch subsequent to either a pressure or volume overload. Many substances locally produced and acting in a paracrine-autocrine fashion are involved in the response to stretch by cardiac cells. The stretch, and, similarly, various growth factors (i.e. angiotensin II. endothelins, transforming growth factor beta, fibroblast growth factors), are able to modulate the expression of several protooncogenes in the cells of the myocardium, and these events are linked to the development of cardiac hypertrophy. Major goals of future research will include the detection of the molecular mechanisms enabling the cardiomyocyte, a terminally differentiated muscle cell, to respond to a mitogenic stimulus with hypertrophic rather than hyperplastic growth, as well as the identification of drugs able to block the evolution of hypertrophy to heart failure.

Adult↗