Transcriptional activation of Mink enteritis virus VP2 by the C-terminal of its NS1 protein

Mink enteritis virus (MEV) NS1 is a multidomain and multifunctional protein containing origin binding, helicase, and transactivation domains. In particular, parvoviral NS1 proteins are transactivators of the viral capsid protein promoter although the manner by which they exert these transactivation effects remained unclear. In this study, the region of the transactivation domain of the NS1 C-terminal was found located at aa 557 ~ 668 and any deletion within this region reduced the transactivation activity. A dominant negative mutation of the 63 aa deletion in the C-terminal of NS1 protein resulted in loss of ability to activate P38 and VP2-5′UTR in a dual-luciferase reporter assay system, a VP2 protein expression system, and within the whole MEV genome, independent of downstream genes. Additionally, a full-length MEV clone deficient in its NS1 C-terminal failed to rescue the virus, possibly due to the loss of integrity of DNA sequences interacting with NS1 protein, and expression of VP2 was also inhibited even when normal NS1 protein was supplied in trans.