Distinct functional role of Hepatitis C virus core protein on NF-κB regulation is linked to genomic variation

Hepatitis C virus (HCV) often causes a prolonged and persistent infection. Sequence divergence in the HCV genome indicates several genotypes and a series of subtypes for this virus. The core protein of HCV has many intriguing functional properties and is implicated as a factor in virus mediated pathogenesis. Nuclear factor κB (NF-κB), a transcription factor, responds to inflammatory signals, activates the expression of inflammatory mediators, and plays a role in cell proliferation process. In this study, we have investigated NF-κB regulation by HCV core protein cloned from three isolates of different genotypes. Our results suggest that core protein from HCV genotype 1a represses NF-κB activation, unlike two other core genomic regions from HCV genotype 1b (BK or Taiwan). However, missense mutations in positions (K9 to R or N11 to T) of HCV genotype 1a relieve repression of NF-κB regulation by core protein. Interestingly, in vitro translation studies suggested that amino acid substitution at position 11 (N→T) in HCV genotype 1a generated a primary protein product of 17 kDa, smaller than the major 21 kDa protein band apparent in the parental sequence or with one carrying mutation at amino acid position 9 (K→R). However, the 17 kDa protein did not appear to be involved in NF-κB regulation. Taken together, our present data suggest that genomic variation in the core protein determines a distinct functional regulation of NF-κB, which may modulate immunnoregulatory molecules early in viral infection.