This study employs time-resolved crystallographic analyses to visualize chemical events accompanying phosphodiester bond formation during DNA synthesis by DNA polymerases (dPols). The authors demonstrate that hydrolysis of the PPi moiety to inorganic phosphate is an intrinsic and critical step of the synthesis reaction, and is a general attribute of DNA synthesis by all dPols. The breakdown of PPi during DNA synthesis by dPols ensures that the synthesis reaction is energetically favorable and moves in the forward direction. This finding provides a solution for a long-standing question regarding the thermodynamics of the DNA synthesis reaction. The same study also indicates that the phosphodiester bond formation involves a mechanism wherein bonds are formed and broken sequentially and not concomitantly. These findings should therefore also be of great interest in an ongoing debate regarding the number and role of Mg2+ ions involved in the reaction utilized by dPols to synthesize DNA.
NAR’s Breakthrough Articles present high-impact studies answering long-standing questions in the field of nucleic acids research and/or opening up new areas and mechanistic hypotheses for investigation. These articles are chosen by the Editors on the recommendation of Editorial Board Members and Referees. Articles are accompanied by a brief synopsis explaining the findings of the paper and where they fit in the broader context of nucleic acids research. They represent the very best papers published at NAR.
FD is a rare inherited disease caused by a single point mutation in the IKBKAP gene that results in defective splicing of its pre-mRNA and reduction of the IKAP protein. Previously, investigators had demonstrated that defective SMN2 splicing could be corrected using an antisense oligonucleotide (ASO), leading to an approved therapy for spinal muscular atrophy. In this manuscript, investigators identified antisense oligonucleotides (‘ASOs’) that correct the splicing of human IKBKAP pre-mRNA and reveal cisregulatory elements that controls its splicing. By systematically screening ASOs with uniformly modified 2’-Omethoxyethylribose (MOE)-phosphate backbone, they identified candidates that enhance retention of exon 20 during pre-mRNA splicing. This work provides deeper insights into the mechanisms of IKBKAP exon 20 splicing and sets the stage for the clinical development of antisense FD therapeutics.
Arginine methylation, which is carried out by at least 9 enzymes in humans, is implicated in the control and regulation of many biological processes. The fraction of arginine residues that are methylated in the human proteome is reported to rival levels of phosphorylated serine and ubiquitinated lysines, and are known to serve as binding sites for various 'reader' proteins. Carm1, also known as PRMT4, was one of the first arginine methytransferase enzymes shown to function as a transcriptional regulator. It is highly expressed in testes and shown to be translocated to the nucleus during spermatid generation, and was therefore hypothesized to play an important role during spermatogenesis. The studies described in this paper provide direct evidence supporting this biological role, as well as mechanistic details into at least some of the interactions and functions of CARM1 in this capacity.
