Modulation of protein synthesis by extracellular matrix: Potential involvement of two nucleolar proteins, nucleolin and fibrillarin

Fibroblasts cultivated in a collagen matrix exhibit a large decrease in the synthesis of most proteins. depending on transcriptional and posttranscriptional controls. Wt have previously shown that ribosomal RNA content and half-life wc rr decreased in collagen lattice cultures. Here, we cultivated human dermal fibroblasts in monolayers and in lattices and studied by competitive RT-PCR analysis the expression of the nucleolar proteins nucleolin and fibrillarin, two key factors in ribosome processing and association. Nucleolin expression was found increased, and fibrillarin expression decreased, in collagen-lattice vs monolayer-cultured fibroblasts, with some variability according to the strains (+25 to +250% and -40 to -60%, respectively). These data suggest that a possible trouble of the association between neosynthesized rRNA and nucleolar proteins is, at least partly, responsible for the inhibition of protein synthesis induced by the extracellular matrix. (C) 1996 Academic Press, Inc.