A functional nuclear localization sequence in the VP1 capsid protein

A functional nuclear localization sequence in the VP1 capsid protein
of coxsackievirus B3
Wang T, Yu B, Lin L, Zhai X, Han Y, Qin Y, Guo Z, Wu S, Zhong X, Wang Y, Tong L, Zhang F, Si X, Zhao W, Zhong Z.
Virology. 2012 Nov 25;433(2):513-21. doi: 10.1016.
Presenter : Yun-Yin Lien
Date/Time : 2013/03/21
16:10 -17:00
Commentator : Dr. Jen-Ren Wang
Location : Room 601,Med College Building
Background :
Coxsackievirus is a small, nonenveloped virus with positive single strand RNA genome. It
belongs to members of Picornaviridae family and is amajor pathogen of human myocarditis and
dilated cardio-myopathy. Coxsackievirus is typified by an icosahedral outer capsid structure
consisting of 60 capsomers that is composed of four structural proteins VP1-VP4. Recent studies
reveal that the capsid proteins of some RNA viruses can translocate to the nucleus and disturb the
nuclear functions. Previous studies showed that the Coxsackievirus VP1 protein not only is a
structural unit of the capsid, but also involves in the viral pathogenesis. However, there is no report
about the CVB VP1 protein translocation from the cytoplasm to the nucleus so far.
To investigate the role of CVB VP1 protein translocate from the cytoplasm to the nucleus.
CVB3 VP1 protein was found mainly located in the nucleus. When expressing two truncated
CVB3 VP1-coding sequences, the authors found that NLS sequence was preliminarily located in the
C-terminal of CVB3 VP1 protein. Four C-terminal truncates of CVB3 VP1 were further generated and
expressed in HeLa cells. The result indicates that NLS sequence was located between Met213 and
Ile275. In addition, two basic amino acids in the NLS were found to be different between CVB3 VP1
and EV71 VP1 protein after sequence alignment. Site-directed mutagenesis was further used to
generate two CVB3 VP1 mutants, and the result shows that the His220 was a key amino acid residue
in the NLS of CVB3 VP1 protein. To understand the functional relevance of these mutations in cell
survival, HeLa cells were transfected with pEGFP-VP1 and pEGFP-VP1H220T and their role in the cell
cycle regulation was determined by flow cytometry. Their results suggest that translocation of CVB3
VP1 to nucleus could sufficiently deregulate the cell cycle.
These results collectively indicated that VP1 protein of CVB3 could specifically localize in the
nucleus through a NLS sequence near its C-terminal. And the nuclear localization of CVB3 VP1
protein could deregulate the cell cycle of the VP1-expressing cells.
References :
1. Colpitts, T.M., Barthel, S., Wang, P., Fikrig, E., 2011. Dengue virus capsid protein binds core
histones and inhibits nucleosome formation in human liver cells. PLoS One 6, e24365.
2. Fairweather, D., Stafford, K.A., Sung, Y.K., 2012. Update on coxsackievirus B3 myocarditis. Curr.
Opin. Rheumatol.