Hydrostatic pressure influences histone mRNA

ABSTRACT Exposure of HeLa S3 cells to high hydrostatic pressure (6.89 ×103 to 6.89 ×104 kPa: 1000 to 10000lbfin-2) reduced core and H1 histone mRNA levels as determined by hybridization to specific histone DNA probes. At 4.14×104kPa for 10 min core histone and H1 histone mRNA levels were reduced 32–38% and 56%, respectively. At 30 min post-decompression core mRNA levels returned to atmospheric control levels while H1 histone mRNA levels continued to be suppressed. Levels of macromolecular synthesis were monitored under hydrostatic pressure with radioactive precursors of RNA, DNA and protein. Macromolecular synthesis was shown to be suppressed in a dose-dependent manner with increasing magnitude and duration of pressure. To determine the influence of pressure on histone mRNA stability, actinomycin D (10 μg ml-1) was used to block RNA synthesis. Relative amounts of H4 and H1 mRNA were determined at atmospheric pressure and following treatment with actinomycin D (10μgml1), pressure (4.14×104kPa) and a combination of pressure and actinomycin D. This study shows that a synthesis component and a stability component are involved in the pressure-induced reduction of core histone mRNA. At 4.14×104kPa for 15 min, there was a 42% reduction in core histone mRNA of which approximately one third was due a suppression of transcription and two thirds to a loss of mRNA stability. The pressure-induced reduction in histone mRNA is attributed to the instability of endogenous histone mRNA and a reduction in transcription/processing of new histone mRNA.