Protein synthesis in bluetongue virus-infected cells.

The first virus-specific proteins in bluetongue virus (BTV)-infected cells can be demonstrated 2 to 4 hr after infection (p.i.) at 31° by immune precipitation. There is a rapid increase in the rate of synthesis until 11 hr p.i. after which synthesis remains at about the same level until 26 hr p.i. Apart from the seven BTV capsid polypeptides, two noncapsid polypeptides P5A and P6A, with respective molecular weights of 54,000 and 40,000 daltons, were identified in the infected cells. Polypeptide P5A is synthesized at a higher rate than any of the others. It is the main if not only component of a complex with an S value slightly less than 400. There is little evidence for specific regulation of the translation process in BTV-infected cells. With the possible exception of polypeptide P1, all the others are translated with a relative frequency that is not significantly different from that of the corresponding mRNA species. Pulse-chase experiments indicate that the BTV polypeptides do not accumulate in the soluble fraction in the same ratio in which they are synthesized. Polypeptide P3 is removed from the soluble protein pool much more rapidly than any of the other capsid polypeptides. These pulse-chase experiments provided no evidence for a precursor-product relationship between any of the BTV polypeptides. The possibility that one of the noncapsid polypeptides, P6A, is a modified form of one of the capsid polypeptides can, however, not be excluded.