Screening for differentially methylated genes among human colorectal cancer tissues and normal mucosa by microarray chip
MOLECULAR BIOLOGY REPORTS
Authors: Chen, Wei; Xiang, Jun; Chen, De-Feng; Ni, Bei-Bei; Chen, Hao; Fan, Xin-Juan; Wang, Pu-Ning; Song, Shun-Xin; Fang, Le-Kun; Xiao, Huan-Yu; Wang, Lei; Wang, Jian-Ping
Abstract
High density DNA methylation microarrays were used to study the differences of gene methylation level in six pairs of colorectal cancer (CRC) and adjacent normal mucosa. We analyzed the profile of methylated genes by NimbleGen Microarray and the biologic functions by NIH-NAVID. In addition, preliminary validation studies were done in six pairs of samples by MSP (methylation-specific PCR). A total of 4,644 genes had a difference in methylation levels. Among them 2,296 were hypermethylated (log2ratio > 1), 2,348 genes were hypomethylated (log2ratio < -1), in which 293 hypermethylated and 313 hypomethylated genes were unmapped according to the NIH-NAVID. All these genes were randomly distributed on all the chromosomes. However, chromosome 1 contained the most of the hypermethylated genes (232 genes), followed by chromosome 19 (149 genes), chromosome 11 (144 genes), chromosome 2 (141 genes), chromosomes 3 (127 genes). Through the analysis of the statistics, There were 2 hypermethylated/3 hypomethylated genes involved in six pairs of samples simultaneously, followed by 10/14 in five samples, 34/37 in four samples, 101/113 in three samples, 341/377 in two samples, 1,808/1,804 in one sample. According to gene ontology analysis, some physiological processes play important roles in the cell division and the development of tumor, such as apoptosis, DNA repair, immune, cell cycle, cell cycle checkpoint, cell adhesion and invasion etc. Through Preliminary validation, there were two genes (St3gal6, Opcml) in thirty top-ranking genes shown hypermethylated in six pairs of CRC and adjacent normal mucosa. Conclusions High density DNA methylation microarrays is an effective method for screening aberrantly methylated genes in CRC. The methylated genes should be further studied for diagnostic or prognostic markers for CRC.
The PRMT5/WDR77 complex regulates alternative splicing through ZNF326 in breast cancer
NUCLEIC ACIDS RESEARCH
Authors: Rengasamy, Madhumitha; Zhang, Fan; Vashisht, Ajay; Song, Won-Min; Aguilo, Francesca; Sun, Yifei; Li, SiDe; Zhang, Weijia; Zhang, Bin; Wohlschlegel, James A.; Walsh, Martin J.
Abstract
We observed overexpression and increased intranuclear accumulation of the PRMT5/WDR77 in breast cancer cell lines relative to immortalized breast epithelial cells. Utilizing mass spectrometry and biochemistry approaches we identified the Zn-finger protein ZNF326, as a novel interaction partner and substrate of the nuclear PRMT5/WDR77 complex. ZNF326 is symmetrically dimethylated at arginine 175 (R175) and this modification is lost in a PRMT5 and WDR77-dependent manner. Loss of PRMT5 or WDR77 in MDA-MB-231 cells leads to defects in alternative splicing, including inclusion of A-T rich exons in target genes, a phenomenon that has previously been observed upon loss of ZNF326. We observed that the alternatively spliced transcripts of a subset of these genes, involved in proliferation and tumor cell migration like REPIN1/AP4, ST3GAL6, TRNAU1AP and PFKM are degraded upon loss of PRMT5. In summary, we have identified a novel mechanism through which the PRMT5/WDR77 complex maintains the balance between splicing and mRNA stability through methylation of ZNF326.