Eukaryotic translation elongation factor 1A exists as two 98 % homologous isoforms: eEF1A1 (A1) and eEF1A2 (A2) which are tissue and development specific. Despite high homology in an open reading frame (ORF) region, mRNAs coding for eEF1A1 and eEF1A2 are different in their untranslated regions (UTR), suggesting a possibility of their dissimilar post-transcriptional regulation. Aim. To analyze the existence of cis-acting motifs in the UTRs of EEF1A1/A2 mRNAs, to confirm the possibility of post-transcriptional control of eEF1A1 and eEF1A2 expression. Methods. An ensemble of bioinformatic methods was applied to predict regulatory motifs in the UTRs of EEF1A1/A2 mRNAs. Dual-luciferase reporter assay was employed to detect post-transcriptional regulation of eEF1A1/A2 expression. Results. Numerous regulatory motifs in the UTR of EEF1A1/A2 mRNAs were found bioinformatically. The experimental evidence was obtained for the existence of negative regulation of EEF1A1 and positive regulation of EEF1A2 mRNA in the model of breast cancer development. Conclusions. EEF1A1 and EEF1A2 mRNAs contain distinct motifs in the UTRs and are differently regulated in cancer suggesting the possibility of their control by different cellular signals

Eukaryotic translation elongation factor 1A (eEF1A) exists as two 98 % homologous isoforms eEF1A1 and eEF1A2 that are tissue/development specific and differentially linked to apoptosis/cancerogenesis. A2 is overexpressed in a number of tumors while unusual expression of A1 is observed in injured muscles. To approach a possible mechanism underlying induced changes in the relative amounts of the isoforms we examined the intrinsic stability of the proteins and their mRNAs in human cancer cells. Aim. To estimate half-life of the isoforms of eEF1A at mRNA and protein level in human cancer cells. Methods. To measure mRNA stability the transcriptional block technique was applied, with subsequent analysis of the mRNA level by qPCR. To determine the protein decay rate the translation was blocked by cycloheximide and changes in the protein level were detected by Western blot. Results. Calculation of the protein stability revealed half-life of 72 for eEF1A1 and 95 hours for eEF1A2. Half-life of EEF1A1 and EEF1A2 mRNAs were 3 and 60 hours respectively. Conclusions. Despite similar protein stability, the isoforms of eEF1A dramatically differ in the half-lives of their mRNAs, suggesting that the mRNA decay mechanism is one of the main regulators of eEF1A1/A2 amount in MCF7 cancer cells