Characterization of the Nuclear Export Signal of Human Papillomavirus 16 L2 Minor Capsid Protein

Abstract

The L2 minor capsid protein of human papillomavirus is one of two structural proteins that comprise the icosahedral shell. Two potential, leucine-rich nuclear export signals (NESs) had been identified in the HPV16 L2 sequence, one in the n-terminus (51MGVFFGGLGI60) and one in the c-terminus (462LPYFFDSVSL471). DNA primers for mutant L2 proteins were designed to specifically target these two potential NES regions. Two primers had mutations in the n-terminal located NES (nNES), while the other two primers had mutations in the c-terminal NES (cNES). L2 nuclear retention mutants, RR297AA (“MS4”) and RTR313AAA (“MS5”), served as the templates for these NES mutations. Using mutagenesis, the desired secondary mutations were introduced into the mutant L2 genes in order to create four, distinct mutants: RR297AA + P463_ (“MS4 T1”), RR297AA + V469_ (“MS4 T2), RTR313AAA + P463_ (“MS5 T1”), and RTR313AAA + V469_ (“MS5 T2”). In contrast to the pancellular localization of the MS4 and MS5 L2 mutants, the “MS4 T1,” “MS4 T2,” “MS5 T1”, and “MS5 T2” mutants were all localized nuclearly. These results suggest that deletion of the cNES inhibits nuclear export of the HPV16 L2 minor capsid protein.