Background: The chromosome 1q12 region harbors the genome’s largest
pericentromeric heterochromatin domain that includes tandemly repeated satellite
III DNA [SatIII (1)]. Increased SatIII (1) copy numbers have been found in
cultured human skin fibroblasts (HSFs) during replicative senescence. The aim of
this study was to analyze the variation in SatIII (1) abundance in cultured HSFs
at early passages depending on the levels of endogenous and exogenous stress.
Methods: We studied 10 HSF cell lines with either high (HSFs from
schizophrenic cases, n = 5) or low (HSFs from healthy controls, n = 5) levels of
oxidative stress. The levels of endogenous stress were estimated by the amounts
of reactive oxygen species, DNA damage markers (8-hydroxy-2-deoxyguanosine,
gamma-H2A histone family member X), pro- and antioxidant proteins (NADPH oxidase
4, superoxide dismutase 1, nuclear factor erythroid 2-related factor 2), and
proteins that regulate apoptosis and autophagy (B-cell lymphoma 2 [Bcl-2],
Bcl-2-associated X protein, light chain 3). SatIII (1) copy numbers were measured
using the nonradioactive quantitative hybridization technique. For comparison,
the contents of telomeric and ribosomal RNA gene repeats were
determined. RNASATIII (1 and 9) were quantified using quantitative Polymerase
Chain Reaction (PCR). Results: Increased SatIII (1) contents in DNA from
confluent HSFs were positively correlated with increased oxidative stress.
Confluent cell cultivation without medium replacement and heat shock induced a
decrease of SatIII (1) in DNA in parallel with a decrease in RNASATIII (1) and an
increase in RNASATIII (9). Conclusions: During HSF cultivation, cells
with increased SatIII (1) content accumulated in the cell pool under conditions
of exaggerated oxidative stress. This fraction of cells decreased after the
additional impact of exogenous stress. The process seems to be oscillatory.
