The demethylase NMAD-1 regulates DNA replication and repair in the Caenorhabditis elegans germline

Abstract

The biological roles of nucleic acid methylation, other than at the C5-position of cytosines in CpG dinucleotides, are still not well understood. Here, we report genetic evidence for a critical role for the putative DNA demethylase NMAD-1 in regulating meiosis in C . elegans . nmad-1 mutants have reduced fertility. They show defects in prophase I of meiosis, which leads to reduced embryo production and an increased incidence of males due to defective chromosomal segregation. In nmad-1 mutant worms, nuclear staging beginning at the leptotene and zygotene stages is disorganized, the cohesin complex is mislocalized at the diplotene and diakinesis stages, and chromosomes are improperly condensed, fused, or lost by the end of diakinesis. RNA sequencing of the nmad-1 germline revealed reduced induction of DNA replication and DNA damage response genes during meiosis, which was coupled with delayed DNA replication, impaired DNA repair and increased apoptosis of maturing oocytes. To begin to understand how NMAD-1 regulates DNA replication and repair, we used immunoprecipitation and mass spectrometry to identify NMAD-1 binding proteins. NMAD-1 binds to multiple proteins that regulate DNA repair and replication, including topoisomerase TOP-2 and co-localizes with TOP-2 on chromatin. Moreover, the majority of TOP-2 binding to chromatin depends on NMAD-1. These results suggest that NMAD-1 functions at DNA replication sites to regulate DNA replication and repair during meiosis.

ALKBH4 promotes tumourigenesis with a poor prognosis in non-small-cell lung cancer

“…Recently, it was reported that ALKBH4 functions as a demethylase for N6-adenosine modification in DNA 39 , and the C. elegans ALKBH4 ortholog (denoted NMAD-1) also has such a demethylase function 40 . Abrogation of ALKBH4 (or NMAD-1) function appears to have strong effects on various phenomena related to cell cycle progression, such as cytokinesis, DNA replication, and meiosis 15 , 41 , 42 . As shown in Supplementary Table S3 , ALKBH4 knockdown also affected DNA replication and meiosis-related genes in A549 cells.…”

Topoisomerases Modulate the Timing of Meiotic DNA Breakage and Chromosome Morphogenesis inSaccharomyces cerevisiae

“…This altered binding suggests that mutant Top2 is no longer efficiently recruited to sites of topological stress but may instead interact with other protein components or chromatin marks of meiotic chromosomes. In this context, it may be significant that S. cerevisiae Top2 shares an acidic patch at its C-terminus that functions as a chromatin-binding domain in mammalian Topo IIα (LANE et al 2013) and that Top2 recruitment to meiotic chromosomes in C. elegans requires a specific chromatin-modifying enzyme (WANG et al 2019).…”

Topoisomerases modulate the timing of meiotic DNA breakage and chromosome morphogenesis inSaccharomyces cerevisiae

“…This repatterning away from promoters suggests that mutant Top2 is no longer efficiently recruited to sites of topological stress but may instead interact with other protein components or chromatin marks of meiotic chromosomes. In this context, it may be significant that S. cerevisiae Top2 shares an acidic patch at its C-terminus that functions as a chromatin-binding domain in mammalian Topo IIα (Lane et al, 2013) and that Top2 recruitment to meiotic chromosomes in C. elegans requires a specific chromatin-modifying enzyme (Wang et al, 2019).…”