DNA mismatch repair (MMR) corrects mispair nucleotides that arise from polymerase misincorporation. Highly conserved MutS (MSH) and MutL (MLH/PMS) homologs initiate MMR, and in higher eukaryotes act as DNA damage sensors that can trigger apoptosis. The MSH proteins recognize the mismatch nucleotides, whereas the MLH/PMS proteins mediate multiple protein–protein interactions associated with downstream MMR events including strand-specific incision and excision. Remarkably, the mechanics of the MSH and MLH/PMS proteins have been elusive for decades. Here we summarize and discuss recent biophysical studies of core MMR components, especially focusing on the unique conformations of MSH and MLH/PMS proteins that lead to the coordination of multiple repair events.
Mitochondria are the only organelles other than the nucleus harboring their DNA in mammalian cells. The mitochondrial DNA (mtDNA) mutation is the cause of many serious diseases, which still lack effective therapies. Our previous report showed that mtDNA mutation exacerbates female reproductive aging. However, the regulation of mtDNA mutation on stem cells is still unknown. Herein, we generated embryonic stem cells (ESCs) harboring massive mtDNA mutations without affecting genomic DNA to study the role of mtDNA mutation in pluripotency. The mtDNA mutation impacted the balance of pluripotency and totipotency of ESCs with a metabolism modulation as the down-regulation of oxidative phosphorylation in energy production, followed by a high level of ROS production by mitochondria. This work would shed light on the investigation and treatment of mtDNA mutant diseases.
Disordered choline metabolism is associated with tumor progression. Glycerophosphocholine phosphodiesterase 1 (GPCPD1) is critical for cleaving glycerophosphocholine (GPC) to produce choline. However, whether and how GPCPD1 is epigenetically regulated remains largely unknown. In the current study, we report that histone H3 lysine 9 (H3K9) methyltransferase GLP (G9a-like Protein) is essential for transcriptional activation of GPCPD1 through H3K9me1 to promote tumor cell migration and invasion. Knocking down GLP or inhibiting its methyltransferase activity impaired GPCPD1 expression and decreased the choline levels. Importantly, we confirmed that both GPCPD1 and choline levels are positively correlated with cancer cell migration. The reduced migration and invasion of GPCPD1-knockdown cells were rescued by choline treatment. Interestingly, GPCPD1 gene expression was found regulated by transcription factor Krüppel-like Factor 5 (KLF5). KLF5 recruitment was GLP-dependent and was indispensable for GPC-induced GPCPD1 expression. These data suggest that GLP promotes tumor cell migration and invasion by transcriptionally activating GPCPD1. GLP and KLF5 are potential therapeutic targets in future cancer treatment.
DNA repair efficiency is an important determinant of oocyte quality and female fertility. DYNLL1 (Dynein light chain 1) plays a part in DNA double-strand break (DSB) repair choice by promoting error-prone non-homologous end joining (NHEJ) repair and in contrast by limiting accurate and error-free homologous recombination (HR) repair. Here, we showed that DYNLL1 transcript abundance decreases gradually during oocyte and follicular growth in mice. In parallel, DYNLL1 mRNA transcript levels decline in the course of oocyte meiotic maturation in mice. Furthermore, our in silico analysis showed that ovaries from high-fertility mice with increased ovulation have lower DYNLL1 transcript abundance compared with that of control mice. Similarly, we found that the induction of ovulation with human chorionic gonadotropin (hCG) decreases DYNLL1 mRNA transcript levels in cumulus oocyte complexes in mice. We hypothesize that this decrease in DYNLL1 transcript abundance during oocyte and follicular growth and in ovulation might lead to relatively higher error-free HR repair and lower error-prone NHEJ repair events in mice, resulting in increased genome stability. Increased genome stability in mice with lower DYNLL1 levels might also contribute to better fertility performance. This paper highlights the need for further in vivo and mechanistic studies to better understand the role of DYNLL1 down-regulation in the maintenance of oocyte reserve and in oocyte quality and fertility.