Transcription activity contributes to the firing of non-constitutive origins in African trypanosomes helping to maintain robustness in S-phase duration

• Published in: Scientific reports Vol. 9; no. 1; pp. 18512 - 19
• Main Authors: da Silva, Marcelo S., Cayres-Silva, Gustavo R., Vitarelli, Marcela O., Marin, Paula A., Hiraiwa, Priscila M., Araújo, Christiane B., Scholl, Bruno B., Ávila, Andrea R., McCulloch, Richard, Reis, Marcelo S., Elias, Maria Carolina
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06-12-2019; Nature Publishing Group
• Subjects: 119/118; 14/19; 14/34; 14/63; 38/1; 38/22; 38/71; 45/47; 631/326/417/1716; 631/326/417/2550; 631/337/1427/2122; 631/337/151/1431; 631/337/151/2355; Cell Cycle; Computer Simulation; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA Damage; DNA Replication; G2 Phase; Genomes; Genomic Instability; Histones - metabolism; Humanities and Social Sciences; Immunofluorescence; Microscopy, Fluorescence; Monte Carlo Method; multidisciplinary; Parasites; Protein Domains; R-loops; Replication; Replication Origin; Replication origins; Ribonucleic acid; RNA; S Phase; Science; Science (multidisciplinary); Stochastic Processes; Transcription; Trypanosoma brucei brucei - genetics; Trypanosoma brucei brucei - metabolism
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-54366-w

The co-synthesis of DNA and RNA potentially generates conflicts between replication and transcription, which can lead to genomic instability. In trypanosomatids, eukaryotic parasites that perform polycistronic transcription, this phenomenon and its consequences are still little studied. Here, we showed that the number of constitutive origins mapped in the
Trypanosoma brucei
genome is less than the minimum required to complete replication within S-phase duration. By the development of a mechanistic model of DNA replication considering replication-transcription conflicts and using immunofluorescence assays and DNA combing approaches, we demonstrated that the activation of non-constitutive (backup) origins are indispensable for replication to be completed within S-phase period. Together, our findings suggest that transcription activity during S phase generates R-loops, which contributes to the emergence of DNA lesions, leading to the firing of backup origins that help maintain robustness in S-phase duration. The usage of this increased pool of origins, contributing to the maintenance of DNA replication, seems to be of paramount importance for the survival of this parasite that affects million people around the world.