The novel human endogenous retrovirus-related gene, psiTPTE22-HERV, is silenced by DNA methylation in cancers.
The psiTPTE22 gene has been designated as a TPTE pseudogene. Our study found that the 5' part of psiTPTE22 has no sequence similarity to TPTE and contains a 3.8-kb human endogenous retrovirus (HERV) element. Because of the HERV element, the 5' part of psiTPTE22 (psiTPTE22-HERV) expresses independently as a gene. Comparison between the DNA sequences of humans and chimps indicated that psiTPTE22-HERV is human specific. We identified 3 alternatively spliced transcript variants from psiTPTE22-HERV by a PCR-based strategy, which use the transcriptional termination signal contained in the HERV element. A 402-nt ORF was contained in the 2 longer transcripts. Western blotting using antibodies produced with chemically synthesized peptide confirmed that a 15-kDa protein was translated from this ORF. RT-PCR results indicated that the ORF-containing transcripts were mainly expressed in psiTPTE22-HERV-expressing samples. Real-time quantitative RT-PCR results showed that expression of the 402-nt ORF was upregulated in normal tissues of kidney, liver, stomach, and lung but downregulated in corresponding tumor tissues. This gene is located near the centromere of chromosome 22 and has a high GC content around the promoter region. Bisulfite sequencing PCR results indicated that it is silenced in cancers by DNA methylation. The expression of psiTPTE22-HERV can be recovered in cancer cells using DNA methylation and histone deacetylase inhibitors. These results suggest psiTPTE22-HERV is regulated epigenetically by DNA methylation. Our study paved the way for further study on an interesting HERV-related human-specific gene, which is silenced in cancers by DNA methylation.
Liang
Qiaoyi
Q
Cancer Institute, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Ding
Jiayi
J
Xu
Rongzhen
R
Xu
Zefeng
Z
Zheng
Shu
S
D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D015153:Blotting, Western; D002892:Chromosomes, Human, Pair 22 / Q000235:genetics; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors; D000077209:Decitabine; D020077:Endogenous Retroviruses / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics*; D009369:Neoplasms / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D051059:PTEN Phosphohydrolase / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D008565:Membrane Proteins; D012333:RNA, Messenger; C012589:trichostatin A; D000077209:Decitabine; D015254:DNA Modification Methylases; C446603:TPTE protein, human; D051059:PTEN Phosphohydrolase; D001374:Azacitidine