La protein is a potent regulator of replication of hepatitis C virus in patients with chronic hepatitis C through internal ribosomal entry site-directed translation.
OBJECTIVE
Translation of hepatitis C virus is an essential step of viral replication and is mediated by an internal ribosome entry site. We previously reported that the hepatitis C virus internal ribosome entry site is most active during the synthetic (S) or mitotic (M) phases and lowest during quiescent (G 0 ) phase. Here, we investigated host factors responsible for the regulation of the hepatitis C virus internal ribosome entry site.


METHODS
We synchronized the cell-cycle progression and evaluated gene-expression dynamics of host factors and kinetics of hepatitis C virus internal ribosome entry site activity in cells at various points during the cell cycle by using a complementary DNA microarray. We also validated the significance of identified host factors on hepatitis C virus replication in vivo.


RESULTS
Hepatitis C virus internal ribosome entry site activity correlated with a gene cluster induced in the S and G 2 /M phases. It is interesting to note that most initiation factors known to bind or interact with the hepatitis C virus internal ribosome entry site [poly(rC)-binding protein 2, polypyrimidine tract binding protein, eukaryotic initiation factor 3, eukaryotic initiation factor 2gamma, eukaryotic initiation factor 2beta, La protein, and heterogenous nuclear ribonucleoprotein L] were induced during the S and G 2 /M phases. Expression of La protein, polypyrimidine tract binding protein, and eukaryotic initiation factor 3 (p116, p170) were predominantly repressed in G 0 phase and induced in S and G 2 /M phases. Suppression or overexpression of La protein and polypyrimidine tract binding protein in RCF-26 significantly changed hepatitis C virus internal ribosome entry site activity. In the livers of patients with chronic hepatitis C, expression of La protein was significantly increased and correlated with the amount of hepatitis C virus RNA.


CONCLUSIONS
Hepatitis C virus uses host factors induced during cell division but not during quiescence for replication. Of these, La protein is a potent regulator and enhances hepatitis C virus replication in regenerating hepatocytes in patients with chronic hepatitis C.
Honda
Masao
M
Department of Gastroenterology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan.
Shimazaki
Takeo
T
Kaneko
Shuichi
S
D001324:Autoantigens; D001483:Base Sequence; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D017931:DNA Primers; D018450:Disease Progression; D015967:Gene Expression Regulation, Viral; D005816:Genetic Complementation Test; D016174:Hepacivirus / Q000502:physiology*; D019698:Hepatitis C, Chronic / Q000235:genetics* / Q000473:pathology; D006801:Humans; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D014176:Protein Biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012261:Ribonucleoproteins / Q000235:genetics*; D012270:Ribosomes / Q000502:physiology* / Q000821:virology; D014779:Virus Replication / Q000502:physiology*; D000097585:SS-B Antigen
D001324:Autoantigens; D017931:DNA Primers; D020319:Oligodeoxyribonucleotides, Antisense; D012261:Ribonucleoproteins; D000097585:SS-B Antigen