Sn. Naryzhny et H. Lee, Protein profiles of the Chinese hamster ovary cells in the resting and proliferating stages, ELECTROPHOR, 22(9), 2001, pp. 1764-1775
Identification and characterization of the proteins that regulate the trans
ition from the resting stage (G0) through G1 to S phase of the cell cycle a
re of central importance to understand the control of cell proliferation an
d chromosome replication. Unlike in lower organisms, where relatively small
numbers of key factors are involved in this process, the factors involved
in the same control mechanisms in mammalian systems are much more complex.
Furthermore, accumulating lines of evidence now suggest that the nuclear ma
trix and chromatin organization also play an essential role for the cell cy
cle control in mammalian cells. To gain a better understanding of the overa
ll dynamics and changes of the protein factors in the context of matrix/chr
omatin organization, we examined the protein profiles of the Chinese hamste
r ovary (CHO) cells in different cell cycle compartments. The methods used
in this study included subcellular fractionations (cytosol, nuclear extract
ion, chromatin, and nuclear matrix), two-dimensional polyacrylamide gel ele
ctrophoresis (2-D PAGE), silver staining, and immunoblotting. As expected,
significant changes of protein profiles were observed when cells entered in
to proliferating stages from GO. Among approximately 1200 protein spots ana
lyzed by 2-D PAGE, at least 12 showed marked increase or decrease at this t
ransitional period. Further cell-cycle progression from G1 to S phase showe
d less dramatic changes of overall protein protile. However, the profile of
certain proteins showed rather dramatic changes of their subcellular local
ization during this transitional period. In particular, the levels of proli
ferating cell nuclear antigen (PCNA) in the nuclear matrix and chromatin dr
amatically increased in mid-G1 and in the beginning of S phase, respectivel
y, while the overall PCNA level was relatively constant throughout the cell
cycle.