Mid to late S-phase replication of the nucleolus in lymphoid human Molt-4 cells.

Indirect immunofluorescence staining of synchronized lymphoid human Molt-4 cells with proliferating cell nuclear antigen autoantibodies specific for cyclin revealed nucleolar staining only in cells in mid to late S-phase. These results together with similar earlier observations in epithelial and fibroblasts cells indicate that this organelle replicates in mid to late S-phase in cultured somatic cells.