Changes in the nuclear distribution of cyclin (PCNA) during S‐phase are not triggered by post‐translational modifications that are expected to moderately affect its charge

Indirect immunofluorescence studies of HeLa cells using PCNA autoantibodies specific for cyclin have revealed striking changes in the nuclear localization of this protein during S-phase. Two-dimensional gel electrophoretic analysis of the [32P]orthophosphate and [35S]methionine labelled proteins from synchronized cells showed that phosphorylation, or other post-translational modifications that are expected to moderately affect the charge of cyclin (acetylation, glycosylation, sialylation, etc.) are not likely part of the mechanism(s) triggering the migration of this protein.