ABSTRACT
Background: The human OCT4 gene, responsible for pluripotency and self-renewal of Embryonic Stem [ES] and Embryonic Carcinoma [EC] cells, can generate several transcripts [OCT4A, OCT4B-variant 2, OCT4B-variant 3, OCT4B-variant 5, OCT4B1, OCT4 B2 and OCT4B3] by alternative splicing and alternative promoters. OCT4A that is responsible for ES and EC cell stemness properties is transcribed from a promoter upstream of Exon1a in those cells. The OCT4B group variants [OCT4B-varianT[2], OCT4Bvariant3, OCT4B-variant5, OCT4B1, OCT4B2 and OCT4B3] are transcribed from a different promoter located in intron 1 and some of them respond to the cell stresses, but cannot sustain the ES/EC cell self-renewal. However, the exact function of OCT4B group variants is still unclear
Methods: In the present study, we employed RT-PCR and sequencing approaches to explore different forms of OCT4 transcripts
Results: Our data revealed that the OCT4B group variants [OCT4B-varianT[2], OCT4 B-variant3, OCT4B1, OCT4B2 and OCT4B3] have longer 5' UTR in the human bladder carcinoma cell line of 5637
Conclusion: These OCT4 variants undergo alternative splicing in their 5' UTR which might exert regulatory roles in transcription and translation mechanisms
ABSTRACT
Background: Alternative splicing is an important mechanism that regulates gene expression and function in human cells. OCT4, a crucial pluripotency marker in embryonic stem/carcinoma cells generates several spliced variants in different cell types and cancers. The expression of OCT4 in cancers has been challenged in many studies. The existence of several OCT4 spliced variants and absence of specific discriminating primers is the main reason of this controversy. Therefore, using specific primers and discriminating OCT4 variants from each other might help to reduce these discrepancies in carcinogenesis and stem cell researches
Methods: 17 various human cancer, pluripotent and normal cells were cultured and their RNAs were extracted. Related cDNAs were synthesized and the expression pattern of OCT4variants was investigated by RT-PCR assay. PCR products were cloned into pTZ57R/T vector and their authenticity was confirmed by DNA sequencing
Results: Expression pattern of OCT4 variants [OCT4A, OCT4B and OCT4B1] was analyzed by RT-PCR assay and the authenticity of PCR products was confirmed by DNA sequencing. A novel spliced variant of OCT4 was discovered and named as OCT4B3. This variant was very similar to OCT4B2 transcript except that 207-nt of exon 1b is lost. Moreover, the expression pattern of OCT4B3 variant was investigated in 17 human cell types, where its expression was only found in astrocytoma and bladder cancer cell types 1321N1 and 5637, respectively
Conclusion: OCT4 variants are differentially expressed in various human cancer cell lines. Moreover, a novel variant of OCT4, OCT4B3, was detected in two human cancer cell lines of bladder carcinoma [5637] and brain astrocytoma [1321N1] for the first time