Microgravity-Induced Alterations in the H3.3B (H3F3B) Gene Expression and the Histone H3 Structure

It has been believed that microgravity directly can modify the structure, function, and morphology of biosystems and numerous researches have been performed to recognize these alterations. Since histone H3 is an essential protein in the field of epigenetics, this research aimed to evaluate the effects of simulated microgravity on the human H3.3B (H3F3B) gene expression and histone H3 structure. The two-dimensional clinostat was applied for simulating microgravity. Analysis of the gene expression by real-time quantitative PCR revealed that simulated microgravity diminished the expression level of H3.3B considerably (P < 0.001). The UV-Visible absorption and extrinsic fluorescence emission results displayed that after 72 h of simulated microgravity the tertiary structure of histone H3 changed and the surface hydrophobicity of the protein incremented remarkably. Nevertheless, circular dichroism (CD) data showed that simulated microgravity did not perturb the secondary structure of histone H3. Collectively, microgravity can strictly affect the gene expression level of H3.3. Furthermore, histone H3 72 h after subjecting to simulated microgravity can exhibit a molten globule structure. The significance of this research lied in the fact that simulating microgravity can be an effective physical force in gene expression regulation and the protein folding process. This finding could help astrobiologists to realize major health risks for astronaut crews and space travelers and reduce these harmful effects. Furthermore, our observations can open fascinating research lines in astrobiology, biophysics, and exobiology.