Effect of growth state and @entity1457 on nucleolar localization of the 110,000-Da @entity1457 protein in XXXX embryo fibroblasts.

@entity1 @entity19 @entity1457 @entity4316 @entity16613
We have shown previously that the @entity1 110,000-Da @entity1457 protein ( @entity16613 ) associates with nucleoli in several cell types and that in 2-day postconfluent @entity19 10T1/2 cells, a segregation of the antigen from the nucleolar phase-dense body is seen (J.R. Subjeck, T. Shyy, J. Shen, and R.J. Johnson. J. Cell Biol. 97: 1389-1395, 1983). Here we further characterize the nucleolar segmentation of @entity16613 in @entity19 10T1/2 and 3T3 cells with respect to the formation of this structure in dense cultures and investigate the behavior of this protein following conditions (serum deprivation, @entity4316 , and @entity1457 ) known to affect the functional and morphological integrity of the nucleolus. It is shown that in addition to its nucleolar locale, an affinity of @entity16613 for the nonnucleolar, nuclear compartment in actively proliferating cells is also observed. When proliferating cells are treated with @entity4316 (1 microgram/ml) for 8 h, @entity16613 separates from the nucleolar phase-dense body to form a fluorescent nucleolar cap which resembles that seen in confluent cultures. This drug also results in a disappearance of @entity16613 from the nucleoplasm. Incubation of cells for 24 h in media without serum also results in the nucleolar segmentation of @entity16613 and a reduction in nucleoplasmic staining. A moderate nonlethal heat treatment does not lead to segmentation of @entity16613 in proliferating cells but conversely results in a transient reversal of segmentation in confluent cultures. Examination of segmented nucleoli of postconfluent cells by immunoelectron microscopy reveals that @entity16613 is associated with the fibrillar component of these nucleoli, the site of ribosomal DNA.
