Vaccinia cores inhibit translation in cell-free protein synthesis systems at two stages: initiation; and, as shown here, elongation. The former effect tends to obscure the latter. Elongation control could, however, be revealed as follows: when, in a reticulocyte of L-cell lysate, initiation was blocked by a drug (edein), the residual [35S]methionine incorporation was severely reduced by the subsequent addition of vaccinia cores. The elongation block could also be demonstrated by analysis of ribosome profiles: treatment with edein alone permitted ribosomal run-off; treatment with either the elongation inhibition anisomycin or with cores preserved the polyribosomes.
