FIG. 5.

β-Actin mRNA remains associated with heavy polysomes during mitosis despite its translation attenuation. (A) Cycling nonsynchronized (NS) or mitotic (8.5 h after block release; M) HeLa cells were labeled for 20 min with [³⁵S]methionine-cysteine; β-actin was immunoprecipitated and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto a nitrocellulose membrane. The autoradiogram shows the labeled proteins (left). The same membrane was probed by Western blot analysis using antibody specific for β-actin (right). (B) Cycling nonsynchronized (NS) or mitotic (M) cells were used for polysomal analysis on sucrose gradients. Total RNA extracted from each of the 23 gradient fractions was subjected to Northern blot analysis using DIG-labeled probe specific for β-actin cDNA. The data shown represent one of three independent similar experiments.