Biomedical subjects

Sandrine Chabas

Publications and source records attributed to Sandrine Chabas.

3 recordsLinked to original sources

PubMed2003

A promoter activity is present in the DNA sequence corresponding to the hepatitis C virus 5' UTR.

The hepatitis C virus (HCV) 5' untranslated region (UTR) has been extensively studied with regard to its internal ribosomal entry site (IRES) activity. In this work we present results suggesting the existence of a strong promoter activity carried by the DNA sequence corresponding to the HCV 5' UTR. This activity was not detected when the HCV 5' UTR sequence was replaced by HCV 3' UTR or poliovirus 5' UTR sequences. These results were further confirmed by using bicistronic constructions. We demonstrated the presence of an mRNA initiated in this 5' UTR sequence and located the initiation site by the 5' RACE method at nucleotide 67. Furthermore, northern experiments and flow cytometry analysis showed the unambiguous activity of such a promoter sequence in stably transfected cells. Our results strongly suggest that the data obtained using bicistronic DNA constructs carrying the HCV 5' UTR should be analyzed not only at the translational but also at the transcriptional level.

5' Untranslated Regions↗

PubMed2003

Antisense oligonucleotides targeted to the domain IIId of the hepatitis C virus IRES compete with 40S ribosomal subunit binding and prevent in vitro translation.

Initiation of protein synthesis on the hepatitis C virus (HCV) mRNA involves a structured element corresponding to the 5' untranslated region and constituting an internal ribosome entry site (IRES). The domain IIId of the HCV IRES, an imperfect RNA hairpin extending from nucleotides 253 to 279 of the viral mRNA, has been shown to be essential for translation and for the binding of the 40S ribosomal subunit. We investigated the properties of a series of antisense 2'-O-methyloligoribonucleotides targeted to various portions of the domain IIId. Several oligomers, 14-17 nt in length, selectively inhibited in vitro translation of a bicistronic RNA construct in rabbit reticulocyte lysate with IC(50)s <10 nM. The effect was restricted to the second cistron (the Renilla luciferase) located downstream of the HCV IRES; no effect was observed on the expression of the first cistron (the firefly luciferase) which was translated in a cap-dependent manner. Moreover, antisense 2'-O-methyloligoribonucleotides specifically competed with the 40S ribosomal subunit for binding to the IRES RNA in a filter- retention assay. The antisense efficiency of the oligonucleotides was nicely correlated to their affinity for the IIId subdomain and to their ability to displace 40S ribosomal subunit, making this process a likely explanation for in vitro inhibition of HCV-IRES-dependent translation.

Base Sequence↗

PubMedDate not supplied

Modulating viral gene expression by aptamers to RNA structures.

Oligonucleotides exhibiting a strong affinity and a high specificity for RNA hairpins were obtained by in vitro selection. Such oligomers give rise to loop-loop complexes with the target hairpins: the trans-activation responsive (TAR) element of the Human Immunodeficiency virus-1 (HIV-1) or subdomains of the Hepatitis C virus (HCV) mRNA. Chemically modified derivatives of an antiTAR aptamer were shown to compete out the binding of the viral protein Tat and to selectively inhibit the in vitro TAR-dependent transcription of a reporter gene. In addition, antisense oligomers derived from sequences selected against the domain IIId of the HCV internal ribosome entry site were shown to specifically block translation both in a cell-free assay and in cultured cells.

Animals↗