Fig. 1

RegCG shows transcriptional activity, which can be improved by the cytomegalovirus (CMV) promoter. a Plot of observed versus expected CpG values (Obs / Exp), calculated by the Gardiner-Garden and Frommer method [15], using the Cpgplot tool from the European Bioinformatics Institute (https://www.ebi.ac.uk/Tools/seqstats/emboss_cpgplot/). The RegCG region is indicated in the inside box. b Schematic representation of the ACTB gene region that contains a CpG island where the promoter, the CpG island, and the region—named RegCG—are indicated. In addition, the CAAT (-1127 pb), CArG (-1099 pb) and TATA (-1066 pb) boxes, the XhoI (-1089 pb) restriction site, the hypothetical proximal TSS, the exon I, the intron I, part of the exon II, and the start codon of the β-actin coding sequence (ATG) are designated. c Schematic representation pGL-promoter reporter vectors derived from pGL4.17 vector containing recombinant promoters. d, and e Transient reporter transcriptional activity of CHO-K1 cells co-transfected with the pGL-promoter vectors which express the firefly luciferase gene, and the normalization pGL4.73 vector, which expresses the renilla luciferase gene. Each promoter is indicated on the x-axis of the graph. Each point represents the activity value, expressed as relative light units (RLU), normalized against renilla activity (Fir/Ren). The RLU measurements were normalized with respect to the average activity of the CMV promoter, which was assigned to a RLU value equal to 1.0. Graphs d) are representative of two experiments with six points per measurement in each one. Graph e) represents the integration of two experiments with three points per measurement in each one normalized through CMV average activity (n = 6). Data are presented as mean values ± standard deviation (S.D.). The one-tailed unpaired t-test, Mann-Whitney test, was used for statistical analysis. * p < 0.05 and ** p < 0.01