In an advance, online publication of Science this week, researchers at the University of California, Berkeley, report their genome-wide evolutionary analysis of DNA methylation in eukaryotes. In quantifying the extent of DNA methylation in 17 eukaryotic genomes, the team found that "gene body methylation is conserved between plants and animals, whereas selective methylation of transposons is not." They authors write that their data indicate that "extant DNA methylation systems are mosaics of conserved and derived features," and that "methylation is an ancient property of eukaryotic genomes."
In Science Signaling this week, a team of investigators present their identification of miR-22, miR-25, and miR-302 as phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-targeting families within nine genomic loci. They also show that miR-22 and miR-106b~25 are "aberrantly overexpressed in human prostate cancer," and that the intronic miR-106b~25 cluster cooperates with MCM7, which subsequently "triggers prostatic intraepithelial neoplasia in transgenic mice." The authors conclude that their study reveals a "proto-oncogenic miRNA-dependent network for PTEN regulation," and defines "the MCM7 locus as a critical factor in initiating prostate tumorigenesis."
An international research team reveals the evolution of the expanded sex-determining genetic locus in the green alga Volvox carteri. "Until now, sex-determining chromosomes had generally been viewed as regions of decay, steadily losing genes that are not involved in sexual reproduction," James Umen, study co-author, says in a statement. "Our study shows the opposite — that such regions can expand and generate new genetic material much more rapidly than the rest of the genome." Their paper, published this week in Science, concludes that "sex-determining loci affect the evolution of both sex-related and non-sex-related genes."
In a Perspectives piece in Science this week, Qinghua Liu and Zain Paroo of the University of Texas Southwestern Medical Center highlight the "Dicer's cut and switch" motif of chromosomal DNA degradation during apoptosis, described by Akihisa Nakagawa et al. elsewhere in the issue. Nakagawa and colleagues report that inactivation of dcr-1 in Caenorhabditis elegans "compromises apoptosis and blocks apoptotic chromosome fragmentation." The authors present data which suggests that the conversion of dicer ribonuclease into an apoptotic deoxyribonuclease is caspase-dependent.