Replication of Western Equine Encephalomyelitis Virus II. Cytoplasmic Structure Involved in the Synthesis and Development of the Virions

Abstract

Analysis of the cytoplasmic fraction of chick embryo cells during the exponential phase of Western equine encephalomyelitis (WEE) virus growth showed that the viral ribonucleic acid (RNA) labeled by a short pulse with 3 H-uridine was associated with a structure which sedimented in sucrose density gradients with a coefficient of 65 S . The RNA extracted from this structure sedimented in sucrose density gradients at 26 S . After a longer period of exposure to 3 H-uridine, the radio-active viral RNA was associated with a structure which sedimented in sucrose density gradients as would materials with coefficients of about 140 S . The 140 S structure contained viral RNA and viral protein. It was shown that the 140 S structures are not virus-induced polysomes. The 140 S structure contained predominantly the 40 S type of viral RNA and some 26 S type. Electrophoretic analysis of the disrupted virion revealed that at least two proteins (types I and II) were present in the purified virion. Only type II protein was present in the 140 S structure. Unlike the virion, the 140 S structure did not contain any lipid which could be detected by the incorporation of 14 C-choline. These data suggest that the 140 S structure represents the internal nucleoprotein part of the virion. The rate of appearance of labeled virus lags behind that of the formation of the 140 S structure in infected cells. Pulse-chase experiments with 3 H-leucine suggest that the 140 S structure may represent a precursor to the virus particle. The results are discussed in terms of the maturation of WEE virus in the infected cells.

Proteins of the Group B Arbovirus Kunjin

“…Most of the 3H-RNA remained associated with some 14C protein in a particle with a sedimentation coefficient of 120S, whereas most of the "4C-protein was released to appear near the top of the gradient in a peak at 10 to 20S. Thus, deoxycholate treatment appears to split the virion producing an RNAprotein "core" particle and protein "envelope" material of much lower S value, in similar fashion to that observed with group A arboviruses (13,16). A small amount of free viral RNA appeared to have been released also, sedimenting slightly faster than the envelope protein.…”

“…Characterization of group A arbovirus proteins by polyacrylamide gel electrophoresis indicates that there are only two, possibly three, structural proteins in the virion and from 5 (with Semliki Forest virus) to 14 (with Sindbis virus) proteins induced in the cytoplasm of infected cells (2,6,7,13,15,16,21). Group B arboviruses are smaller and comprise a larger, more complex group of viruses (1,3).…”

Ribonuclease Sensitivity of Semliki Forest Virus Nucleocapsids

“…The RNA within nucleocapsids of two other group A arboviruses, Westem equine encephalitis virus (16) and Sindbis virus (4,17), has also been reported to be digested by ribonuclease treatment. Sensitivity of the RNA within Semliki Forest virus ntucleocapsids to digestion by ribonuclease.…”

Intracellular Components Associated with Chikungunya Virus‐Specific Ribonucleic Acids in Infected BHK21 Cells1

“…It has been reported that there is a 130-140 S structure containing 40-45 S virion RNA in cells infected with group A arboviruses [2,5,8,27] including Chikungunya virus [15]. This structure corresponds to nucleocapsid (NC) of the virion in respect to its protein subunit [6,17,27], ability to yield infective RNA [5,15], morphology [8,16], and its role as a precursor of the virion as determined in pulse-chase experiments [14,27]. Besides NC, there exists a 65 S component which contained single-stranded 26 S virus-specific RNA [2,5,8,27].…”

“…This structure corresponds to nucleocapsid (NC) of the virion in respect to its protein subunit [6,17,27], ability to yield infective RNA [5,15], morphology [8,16], and its role as a precursor of the virion as determined in pulse-chase experiments [14,27]. Besides NC, there exists a 65 S component which contained single-stranded 26 S virus-specific RNA [2,5,8,27]. These were suspected to be precursors of NC and virion RNA, respectively [4,5,10].…”