ELECTRON-MICROSCOPIC EVIDENCE FOR BUDDING PROCESS-INDEPENDENT ASSEMBLY OF DOUBLE-SHELLED ROTAVIRUS PARTICLES DURING PASSAGE THROUGH ENDOPLASMIC-RETICULUM MEMBRANES

Slowing down of the maturation process of human rotavirus particles on ice allowed the clear demonstration of two different assembly pathway s through the endoplasmic reticulum (ER) membrane. One was the 'envelo ped' and single-shelled (ss) particle assembly pathway, in which a tra nsient envelope is acquired through the budding of subviral particles from the cytoplasm to the ER lumen, and later these 'enveloped' partic les are released as ss particles in the ER lumen. The other was a doub le-shelled particle assembly pathway by which subviral particles acqui re the outer capsid proteins during their transport across the ER memb rane.