In 2003, Acanthamoeba polyphaga mimivirus (APMV) was discovered as parasitizing Acanthamoeba. It was revealed to exhibit remarkable features, especially odd genomic characteristics, and founded viral family Mimiviridae. Subsequently, a second family of giant amoebal viruses was described, Marseilleviridae, whose prototype member is Marseillevirus, discovered in 2009. Currently, the genomes of seven different members of this family have been fully sequenced. Previous phylogenetic analysis suggested the existence of three Marseilleviridae lineages: A, B and C. Here, we describe a new member of this family, Brazilian Marseillevirus (BrMV), which was isolated from a Brazilian sample and whose genome was fully sequenced and analyzed. Surprisingly, data from phylogenetic analyses and comparative genomics, including mean amino acid identity between BrMV and other Marseilleviridae members and the analyses of the core genome and pan-genome of marseilleviruses, indicated that this virus can be assigned to a new Marseilleviridae lineage. Even if the BrMV genome is one of the smallest among Marseilleviridae members, it harbors the second largest gene content into this family. In addition, the BrMV genome encodes 29 ORFans. Here, we describe the isolation and genome analyses of the BrMV strain, and propose its classification as the prototype virus of a new lineage D within the family Marseilleviridae.

For many years, gene expression in the three cellular domains has been studied in an attempt to discover sequences associated with the regulation of the transcription process. Some specific transcriptional features were described in viruses, although few studies have been devoted to understanding the evolutionary aspects related to the spread of promoter motifs through related viral families. The discovery of giant viruses and the proposition of the new viral order Megavirales that comprise a monophyletic group, named nucleo-cytoplasmic large DNA viruses (NCLDV), raised new questions in the field. Some putative promoter sequences have already been described for some NCLDV members, bringing new insights into the evolutionary history of these complex microorganisms. In this review, we summarize the main aspects of the transcription regulation process in the three domains of life, followed by a systematic description of what is currently known about promoter regions in several NCLDVs. We also discuss how the analysis of the promoter sequences could bring new ideas about the giant viruses’ evolution. Finally, considering a possible common ancestor for the NCLDV group, we discussed possible promoters’ evolutionary scenarios and propose the term “MEGA-box” to designate an ancestor promoter motif (‘TATATAAAATTGA’) that could be evolved gradually by nucleotides’ gain and loss and point mutations.

The monkeypox virus (MPXV) is an emerging zoonotic pathogen responsible for mpox, a disease characterized by some smallpox-like symptoms, typically mild but occasionally fatal. The largest mpox recorded global outbreak began in May 2022, with over 162,000 cases across 140 countries. Herein, we have analyzed the intra-clonal diversity of MPXV obtained from a single skin lesion sample from a male patient (June 2022). Three viral clones were obtained following phenotypic evaluation of MPXV lysis plaque characteristics over a three-course infection in BSC-40 cells. Unlike the vaccinia virus Western Reserve (VACV-WR) strain, MPXV clones did not produce comet-like structures, suggesting reduced extracellular enveloped virus (EEV) morphotype release, which is associated with viral dissemination. Whole-genome sequencing and assembly identified subtle differences among clones. Comparative genomic analyses, including synteny and single nucleotide variation (SNV) calling, revealed intra-clonal differences and divergence from clade I and II references, although the variety of mutations found did not reveal possible variations at the protein level. Altogether, these findings suggest that although similar, it is possible that distinct MPXV variants may circulate together and can be found in a single exanthematous lesion.