Measurements of HBV viral load and genotype may help to define which male HBV carriers aged 30 years or older are at high risk for HCC.

Coronaviruses contain a positive-sense singlestranded genomic (g) RNA, which encodes nonstructural proteins. Several subgenomic mRNAs (sgmRNAs) encoding structural proteins are generated by template switching from the body transcription regulatory sequence (TRS) to the leader TRS. The process preferentially generates shorter sgmRNA. Appropriate readthrough of body TRSs is required to produce longer sgmRNAs and full-length gRNA. We find that phosphorylation of the viral nucleocapsid (N) by host glycogen synthase kinase-3 (GSK-3) is required for template switching. GSK-3 inhibition selectively reduces the generation of gRNA and longer sgmRNAs, but not shorter sgmRNAs. N phosphorylation allows recruitment of the RNA helicase DDX1 to the phosphorylated-N-containing complex, which facilitates template readthrough and enables longer sgmRNA synthesis. DDX1 knockdown or loss of helicase activity markedly reduces the levels of longer sgmRNAs. Thus, coronaviruses employ a unique strategy for the transition from discontinuous to continuous transcription to ensure balanced sgmRNAs and full-length gRNA synthesis.

Early detection of SARS-CoV in throat wash and saliva suggests that these specimens are ideal for SARS diagnosis.

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Men have a higher incidence of hepatocellular carcinoma (HCC) than women. Epidemiologic and animal studies have suggested that it might be due to the stimulatory effects of androgen and the protective effects of estrogen. Recently, increasing molecular mechanisms underlying the carcinogenic effect of both sex hormones were reported. Knockout of androgen receptor (AR) expression in hepatocytes delayed the development of N′,N′-diethylnitrosamine (DEN)-induced HCC, suggesting the active AR pathway in augmenting the HCC risk. Moreover, an intriguing interaction between the viral protein of hepatitis B virus X protein (HBx) and the androgen pathway was established. HBx can enhance the transcriptional activity of AR in a ligand concentration-dependent manner, mainly through its effects on the c-Src and GSK-3β kinase pathways. The studies from the DEN-induced HCC mouse model further provided a mechanism for the protective role of estrogen in female HCC. Estrogen can protect hepatocytes from malignant transformation via downregulation of IL-6 release from Kupffer cells, a critical process in this mouse model. Intriguingly, suppression of the ERα protein by overexpression of miR-18a, which occurs preferentially in female HCC, was identified as a novel mechanism to block the tumor-protective function of estrogen in female HCC. In conclusion, the current studies demonstrated that the gender disparity of HCC is attributed by both androgen and estrogen sex hormone pathways, with distinct roles in each gender. Therefore, the ligand and the receptor factors of both sex hormones need to be included for assessing the relative risk of HCC patients of each gender.

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) occurs more often in men than in women. Male HBV carriers usually have higher viral loads, which is a well-known risk factor for HCC. Whether and how the male androgen axis regulates HBV transcription and replication is investigated here. We used HBV transgenic mice to evaluate any sex disparity of serum hepatitis B surface antigen and HBV titers as well as the castration effect on this disparity. Compared to females, HBV transgenic male mice showed higher hepatitis B surface antigen and viral titers, which were lessened by castration of the males. In a cell culture system, HepG2 cells transfected with HBV and androgen receptor (AR) constructs were used to study the effect of the androgen pathway on viral transcription and replication. H epatitis B virus (HBV) chronically infects more than 350 million people worldwide and is a major risk factor for the development of liver cirrhosis and hepatocellular carcinoma (HCC). 1 The prevalence of chronic HBV infection in children has declined (Ͼ90%) following universal immunization. 2 However, adult HBV carriers still have a significant risk for HCC, especially those in areas where HBV infection is endemic. Investigation of mechanisms of HBV infection for HCC may discover new approaches to reduce the risk.Large cohort studies have identified risk factors for HBVrelated HCC, including old age, higher viral titer, diabetes, familial history of HCC, and the male sex. 3,4 The mechanisms of male susceptibility to HCC after HBV infection have been an important topic for study. Both higher androgen levels and more active androgen receptor (AR) gene alleles correlated with an increased risk of HCC among male hepatitis B surface antigen (HBsAg) carriers. 5,6 In AR knockout mice, the development of chemically induced HCC was delayed and the mice had fewer tumors. 7 These studies indicate that the AR axis is involved in hepatocarcinogenesis, and an active AR pathway may augment HCC risk. Consistent with this, we recently showed that HBV X protein (HBx) can enhance the transcriptional activity of AR in a ligand concentration-dependent manner, which may explain the male predominance of HBV-related HCC. 8 Because of the

Viral proteases are essential for pathogenesis and virulence of severe acute respiratory syndrome coronavirus (SARS-CoV). Little information is available on SARS-CoV papain-like protease 2 (PLP2), and development of inhibitors against PLP2 is attractive for antiviral therapy. Here, we report the characterization of SARS-CoV PLP2 (from residues 1414 to 1858) purified from baculovirus-infected insect cells. We demonstrate that SARS-CoV PLP2 by itself differentially cleaves between the amino acids Gly180 and Ala181, Gly818 and Ala819, and Gly2740 and Lys2741 of the viral polypeptide pp1a, as determined by reversed-phase high-performance liquid chromatography analysis coupled with mass spectrometry. This protease is especially selective for the P1, P4, and P6 sites of the substrate. The study demonstrates, for the first time among coronaviral PLPs, that the reaction mechanism of SARS-CoV PLP2 is characteristic of papain and compatible with the involvement of the catalytic dyad (Cys)-S(-)/(His)-Im(+)H ion pair. With a fluorogenic inhibitor-screening platform, we show that zinc ion and its conjugates potently inhibit the enzymatic activity of SARS-CoV PLP2. In addition, we provided evidence for evolutionary reclassification of SARS-CoV. The results provide important insights into the biochemical properties of the coronaviral PLP family and a promising therapeutic way to fight SARS-CoV.