Translocation of hepatitis B virus core particles through nuclear pores in transformed yeast cells

In our previous transmission electron microscopic study of hepatitis B virus core antigen in transformed yeast cells, we observed core particles passing through the nuclear pores. We have now analyzed 1,421 nuclear pores in transformed yeast, and conclude that 1) translocation of core particles from the nucleus to the cytoplasm occurs through the nuclear pores; 2) translocation sites are located in the center of nuclear pores; 3) at least 95% of pores are involved in the translocation process; 4) proteins as large as 28 nm in diameter can cross the envelope; 5) translocation does not stop, but rather becomes more active during nuclear division in yeast cells.