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Effects of serum and conditioned medium on protein degradation, migration of nonhistone proteins to the nucleus, and DNA synthesis in transformed cells
Author(s) -
Polet Herman,
Swager Jeffrey S.
Publication year - 1987
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041300318
Subject(s) - nucleus , non histone protein , dna , degradation (telecommunications) , chemistry , dna synthesis , microbiology and biotechnology , biochemistry , biology , chromatin , computer science , telecommunications
Stimulation of resting transformed cells (Chang liver cells), prelabeled with [ 3 H] leucine, with fetal calf serum, caused increased nuclear translocation of [ 3 H] nonhistone proteins ([ 3 H] NHP) and DNA synthesis and a parallel inhibition of proteolysis of cellular proteins. [ 3 H] NHP migration was independent of protein synthesis. Fractionation of the nuclear proteins in a pH gradient of 2.5–6.5, showed that [ 3 H] NHP fractions with high degradation rates in resting cells corresponded to the [ 3 H] NHP fractions with high migration rates in stimulated cells, suggesting that degradation and migration of [ 3 H] NHP are linked. Conditioned medium (COM) produced by Chang cells had similar effects as serum, suggesting that factors produced by these transformed cells, control cell growth by a mechanism that is similar to serum. The lysosomotropic amine eserine had similar effects as serum and COM. Based on the similarity of the effects, it would appear that serum and COM inhibit lysosomal proteolysis. It is proposed that serum and COM induce NHP migration to the nucleus by inhibiting lysosomal degradation of these proteins. Serum and COM caused also migration of [ 3 H] histones to the nucleus, however the mechanism is not clear.