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DNA methylation plays crucial roles in chromatin structure and gene expression. Aberrant DNA methylation patterns, including global hypomethylation and regional hypermethylation, are associated with cancer and implicated in oncogenic events. How DNA methylation is regulated in developmental and cellular processes and dysregulated in cancer is poorly understood. Here, we show that PRMT6, a protein arginine methyltransferase responsible for asymmetric dimethylation of histone H3 arginine 2 (H3R2me2a), negatively regulates DNA methylation and that PRMT6 upregulation contributes to global DNA hypomethylation in cancer. Mechanistically, PRMT6 overexpression impairs chromatin association of UHRF1, an accessory factor of DNMT1, resulting in passive DNA demethylation. The effect is likely due to elevated H3R2me2a, which inhibits the interaction between UHRF1 and histone H3. Our work identifies a mechanistic link between protein arginine methylation and DNA methylation, which is disrupted in cancer. [ABSTRACT FROM AUTHOR]

Summary Proper telomere length is essential for embryonic stem cell (ESC) self-renewal and pluripotency. Mouse ESCs (mESCs) sporadically convert to a transient totipotent state similar to that of two-cell (2C) embryos to recover shortened telomeres. Zscan4, which exhibits a burst of expression in 2C-like mESCs, is required for telomere extension in these cells. However, the mechanism by which Zscan4 extends telomeres remains elusive. Here, we show that Zscan4 facilitates telomere elongation by inducing global DNA demethylation through downregulation of Uhrf1 and Dnmt1, major components of the maintenance DNA methylation machinery. Mechanistically, Zscan4 recruits Uhrf1 and Dnmt1 and promotes their degradation, which depends on the E3 ubiquitin ligase activity of Uhrf1. Blocking DNA demethylation prevents telomere elongation associated with Zscan4 expression, suggesting that DNA demethylation mediates the effect of Zscan4. Our results define a molecular pathway that contributes to the maintenance of telomere length homeostasis in mESCs. [ABSTRACT FROM AUTHOR]

Abstract: In order to get more insight into its evolution and geographical distribution, we investigated the Leishmania (Viannia) braziliensis species complex using amplified fragment length polymorphisms and sequencing of a heat-shock protein 70 gene fragment. Previously, several assays had alluded to the high genetic diversity of the group, and single-locus assays typically identified two species, i.e. L. braziliensis and Leishmania peruviana, with occasional genetic signatures of both in the same strain. By analysis of 53 parasite isolates from Peru, and eight additional ones from other countries, we identified an atypical L. braziliensis cluster, and confirmed the origin of L. peruviana from the L. braziliensis cluster during the colonization of the western Andean coastal valleys. We discuss the clinical and taxonomical implications of our findings in relation to currently used species typing assays. [Copyright &y& Elsevier]

Abstract: The heat-shock protein 70 gene (hsp70) has been exploited for Leishmania species identification in the Old and New World, using polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis. Three new Leishmania-specific hsp70 PCRs were recently described, and we applied 2 of these on 89 clinical samples from a total of 73 Peruvian patients with either cutaneous or mucocutaneous leishmaniasis. The new PCRs on average showed a 2- to 3-fold improved sensitivity in the tested sample types (lesion biopsies, aspirates, and scrapings), for both genus detection and species typing, and were most successful in biopsies. Leishmania braziliensis, L. peruviana, and L. guyanensis were encountered. About one third of the L. braziliensis parasites contained 2 hsp70 alleles. This study is a paradigm for the implementation of a globally applicable upgraded tool for the identification of Leishmania directly on human specimens from cutaneous and mucocutaneous lesions in the New World. [Copyright &y& Elsevier]

Set7/9 (also known as Set7, Set9, Setd7, and Kmt7) is a lysine methyltransferase that catalyzes the methylation of multiple substrates, including histone H3 and non-histone proteins. Although not essential for normal development and physiology, Set7/9-mediated methylation events play important roles in regulating cellular pathways involved in various human diseases, making Set7/9 a promising therapeutic target. Multiple Set7/9 inhibitors have been developed, which exhibit varying degrees of potency and selectivity in vitro. However, validation of these compounds in vivo has been hampered by the lack of a reliable cellular biomarker for Set7/9 activity. Here, we report the identification of Rpl29, a ribosomal protein abundantly expressed in all cell types, as a major substrate of Set7/9. We show that Rpl29 lysine 5 (Rpl29K5) is methylated exclusively by Set7/9 and can be demethylated by Lsd1 (also known as Kdm1a). Rpl29 is not a core component of the ribosome translational machinery and plays a regulatory role in translation efficiency. Our results indicate that Rpl29 methylation has no effect on global protein synthesis but affects Rpl29 subcellular localization. Using an Rpl29 methylation-specific antibody, we demonstrate that Rpl29K5 methylation is present ubiquitously and validate that (R)-PFI-2, a Set7/9 inhibitor, efficiently reduces Rpl29K5 methylation in cell lines. Thus, Rpl29 methylation can serve as a specific cellular biomarker for measuring Set7/9 activity. [ABSTRACT FROM AUTHOR]

PRMT5 is the primary enzyme responsible for the deposition of the symmetric dimethylarginine in mammalian cells. In an effort to understand how PRMT5 is regulated, we identified a threonine phosphorylation site within a C-terminal tail motif, which is targeted by the Akt/serum- and glucocorticoid-inducible kinases. While investigating the function of this posttranslational modification, we serendipitously discovered that its free C-terminal tail binds PDZ domains (when unphosphorylated) and 14-3-3 proteins (when phosphorylated). In essence, a phosphorylation event within the last few residues of the C-terminal tail generates a posttranslational modification-dependent PDZ/14-3-3 interaction "switch." The C-terminal motif of PRMT5 is required for plasma membrane association, and loss of this switching capacity is not compatible with life. This signaling phenomenon was recently reported for theHPVE6 oncoprotein but has not yet been observed for mammalian proteins. To investigate the prevalence of PDZ/14-3-3 switching in signal transduction, we built a protein domain microarray that harbors PDZ domains and 14-3-3 proteins. We have used this microarray to interrogate the C-terminal tails of a small group of candidate proteins and identified ERBB4, PGHS2, and IRK1 (as well as E6 and PRMT5) as conforming to this signaling mode, suggesting that PDZ/14-3-3 switching may be a broad biological paradigm. [ABSTRACT FROM AUTHOR]