Hydroxymethylated-P16 Allele Is Transcription-Inactive

Abstract

6 # Equal contribution 7 * Corresponding authors 8 Author contributions 9 YG and PL: elucidated the biological function of P16 hydroxymethylation; SQ: discovered 10 P16 hydroxymethylation and its association with gastric carcinogenesis; XH: demonstrated 11 the strand-bias distribution of 5hmCs in the P16 alleles; CC, Z-mL, and BZ: constructed the 12 P16-specific oxygenase; LG performed the animal experiments; BZ performed 13 immunostaining and cell sorting assays and codesigned the study; ZL and JZ: carried out 14 other experiments; DD: designed the study, analyzed the data, and wrote the manuscript. 15 All authors read and approved the final manuscript. 16 Running title: DNA hydroxymethylation does not reactivate gene transcription 17 18 2 ABSTRACT 19 Background: 5-Methylcytosine can be oxidized into 5-hydroxymethylcytosine (5hmC) in 20 the genome. Methylated-P16 (P16M) can be oxidized into completely 21 hydroxymethylated-P16 (P16H) in human cancer and precancer cells. The aim of this study 22 is to investigate the biological function of P16H. 23 Methods: True P16M and P16H were analyzed using bisulfite/TAB-based assays. A 24 ZFP-based P16-specific dioxygenase (P16-TET) was constructed and used to induce 25 P16H. Cell proliferation and migration were determined with a series of biological analyses.26 Results: (A) The 5hmCs were enriched in the antisense-strand of the P16 exon-1 in 27 HCT116 and AGS cells containing methylated-P16 alleles (P16M). (B) P16-TET induced 28 both P16H and P16 demethylation in H1299 and AGS cells and reactivated P16 expression.29Notably, P16H was only detectable in the sorted P16-TET H1299 and AGS cells that did not 30 show P16 expression. (C) P16-TET significantly inhibited the xenograft growth derived from 31 H1299 cells in NOD-SCID mice, but did not inhibit the growth of P16-deleted A549 control 32 cells. P16-siRNA knockdown could rescue P16-TET-inhibited cell migration. 33 Conclusion: Hydroxymethylated P16 alleles are transcriptionally inactive.34 35 36 3 AUTHOR SUMMARY 37 It is well known that 5-methylcytosine (5mC) in genomic DNA of mammalian cells can be 38 oxidized into 5-hydroxymethylcytosine (5hmC) and other derivates by DNA dioxygenase 39 TETs. While conversion of 5mC to 5hmC plays an important role in active DNA 40 demethylation through further oxidations, a certain proportion of 5hmCs remain in the 41 genome. Although it is supposed that occurrence of 5hmCs may contribute to the flexibility 42 of chromatin and the protection of the bivalent promoters from hypermethylation, the direct 43 effect of 5hmCs on gene transcription is unknown. In the present study, we engineered a 44 zinc-finger protein-based P16-specific DNA dioxygenase and used it to induce P16 45 hydroxymethylation and demethylation in cancer cells. Our results demonstrate, for the first 46 time, that the hydroxymethylated P16 alleles retain transcriptionally inactive. This is 47 54It is well known that ten-eleven translocation methylcytosine dioxygenases (TET-1/2/3) 55 oxidize 5-methylcytosine (5mC) to 5-hydrox...

P16 Methylation Leads to Paclitaxel Resistance of Advanced Non-Small Cell Lung Cancer

“…To induce demethylation of P16 CpG islands, an engineered P16-specific dioxygenase (P16-TET) pTRIPZ vector 29 was constructed by fusing a SP1-like engineered seven-zinc finger protein (7ZFP) capable of specifically binding the 21 bp fragment (5'-GAG GAA GGA AAC GGG GCG GGG -3', including a Sp1-binding site ) within the human P16 promoter with the catalytic domain (CD: 1418aa-2136aa) of TET1 (NM_030625.2), and then inserted into the expression controllable pTRIPZ vector carrying a Tet-on' switch (Open Biosystem, USA) to control the expression of the P16-TET. The P16-TET stably transfected H1299 cells were treated with the doxycycline (final conc.…”