tailieunhanh - Báo cáo khoa học: Expression studies of the core+1 protein of the hepatitis C virus 1a in mammalian cells

Recent studies have suggested the existence of a novel protein of hepati-tis C virus (HCV) encoded by an ORF overlapping the core gene in the +1 frame (core+1 ORF). Two alternative translation mechanisms have been proposed for expression of the core+1 ORF of HCV-1a in cultured cells; a frameshift mechanism within codons 8–11, yielding a protein known as core+1⁄F, and⁄or translation initiation from internal codons in the core+1 ORF, yielding a shorter protein known as core+1⁄S. | ỊFEBS Journal Expression studies of the core 1 protein of the hepatitis C virus 1a in mammalian cells The influence of the core protein and proteasomes on the intracellular levels of core 1 Niki Vassilaki Haralabia Boleti and Penelope Mavromara Molecular Virology Laboratory Hellenic Pasteur Institute Athens Greece Keywords core 1 ORF core 1 F protein core 1 S protein frameshift hepatitis C Correspondence P. Mavromara Molecular Virology Laboratory Hellenic Pasteur Institute 127 Vas. Sofias Ave Athens 11521 Greece Fax 30 210 647 8877 Tel 30 210 647 8875 E-mail penelopm@ Received 20 April 2007 revised 8 June 2007 accepted 11 June 2007 doi Recent studies have suggested the existence of a novel protein of hepatitis C virus HCV encoded by an ORF overlapping the core gene in the 1 frame core 1 ORF . Two alternative translation mechanisms have been proposed for expression of the core 1 ORF of HCV-1a in cultured cells a frameshift mechanism within codons 8-11 yielding a protein known as core 1 F and or translation initiation from internal codons in the core 1 ORF yielding a shorter protein known as core-1 S. To date the main evidence for the expression of this protein in vivo has been the specific humoral and cellular immune responses against the protein in HCV-infec-ted patients inasmuch as its detection in biopsies or the HCV infectious system remains elusive. In this study we characterized the expression properties of the HCV-1a core 1 protein in mammalian cells in order to identify conditions that facilitate its detection. We showed that core 1 S is a very unstable protein and that expression of the core protein in addition to proteosome activity can downregulate its intracellular levels. Also we showed that in the Huh-7 T7 cytoplasmic expression system the core 1 ORF from the HCV-1 isolate supports the synthesis of both the core-1 S and core 1 F proteins. Finally immunofluorescence and subcellular fractionation analyses indicated