Role of eIF3a in regulating cisplatin sensitivity and in translational control of nucleotide excision repair of nasopharyngeal carcinoma.

Translational control at the initiation step has been recognized as a major and important regulatory mechanism of gene expression. Eukaryotic initiation factor-3a (eIF3a), a putative subunit of the eIF3 complex, has recently been shown to have an important role in regulating the translation of a subset of mRNAs and is found to correlate with the prognosis of cancers. In this study, using nasopharyngeal carcinoma (NPC) cells as a model system, we tested the hypothesis that eIF3a negatively regulates the synthesis of nucleotide excision repair (NER) proteins, and, in turn, cellular response to treatments with DNA-damaging agents such as cisplatin (cis-dichlorodiammine platinum(II) (CDDP)). We found that a CDDP-sensitive sub-clone S16 isolated through limited dilution from an NPC cell line CNE-2 has increased eIF3a expression. Knocking down its expression in S16 cells increased cellular resistance to CDDP, NER activity and synthesis of the NER proteins XPA, XPC, RAD23B and RPA32. Altering eIF3a expression also changed the cellular response to CDDP and UV treatment in other NPC cell lines. Taken together, we conclude that eIF3a has an important role in the CDDP response and in NER activity of NPCs by suppressing the synthesis of NER proteins.