DciA helicase operators exhibit diversity across bacterial phyla


A fundamental requirement for life is replication of an organism’s DNA. Studies in Escherichia coli and Bacillus subtilis have set the paradigm for how DNA replication occurs in bacteria. During replication initiation in E. coli and B. subtilis, the replicative helicase is loaded onto the DNA at the origin of replication by an ATPase helicase loader. However, most bacteria do not encode homologs to the helicase loaders in E. coli and B. subtilis, raising the question of how helicase activity is facilitated in other bacteria during DNA replication initiation. Recent work has identified the DciA protein as a predicted helicase operator that may perform a function analogous to the helicase loaders in E. coli and B. subtilis. DciA proteins are defined by the presence of a DUF721 domain and are conserved in most bacteria. However, we find that the sequence conservation between DciA proteins across different phyla is very low. Therefore, to comprehensively define the DciA protein family, we took a computational evolutionary approach. These analyses identified diversity in sequence features and domain architectures amongst DciA homologs that were associated with specific phylogenetic lineages. The diversity of DciA proteins elucidated here represents the evolution of helicase operation in bacterial DNA replication, highlights the need for phyla-specific analyses of this fundamental biological process, and is an important example of how research in bacterial DNA replication is necessary in organisms beyond E. coli and B. subtilis.