Chromatin marks associated with recombinant mRNA expression in PT1-CHO cell lines. a ChIP with H2A indicating higher nucleosome occupancy correlating with lower recombinant mRNA expression. Results are presented as percentage input calculated from Ct values, and the means and SEM of n = 12 independent experiments involving four primer pairs along two predicted nucleosome positions in the EEF1A1 promoter region. Also shown are the qPCR values obtained in the four primer pairs for IgG, which served as a control for the ChIP experiment. Statistical significance (*, ***) at P < 0.05, unpaired t test, one-tailed. b H3.3 and H3K9ac enrichments relative to H2A. c A summary of ChIP enrichments for all the analyzed histone variants (H2A.Z, H3.3) and histone modifications (H3K4me3, H3K27me3, H3K9ac, H3K9me3). Data represent means and standard error of the means (SEM) of n = 3 independent experiments and in chromatin isolated at different passages (P52 – P70).