Exonuclease processivity of archaeal replicative DNA polymerase in association with PCNA is expedited by mismatches in DNA

Isolation and Characterization of a Novel myovirus Infecting Shigella dysenteriae from the Aeration Tank Water

The genome sequence, morphology, and genetic features of a novel phage, named SSE1, is reported here. Phage SSE1 that infects Shigella dysenteriae (China General Microbiological Culture Collection Center number: 1.1869) was isolated from the aeration tank water of a sewage treatment plant. SSE1 showed morphological features associated with those of phages in Myoviridae. The whole genome sequence of phage SSE1 is composed of 169,744 bp with the GC content of 37.51%. The double-stranded DNA of SSE1 contains 270 open reading frameworks (ORFs). Phylogenetically, phage SSE1 showed a stronger homology (whole genome and terminase large subunit protein sequence) to Escherichia phages than other Shigella phages in the NCBI database, but SSE1 did not infect Escherichia stains. This indicates that phage SSE1 should be a novel phage infecting Shigella dysenteriae. Besides, the result of this study provided a new idea for phage therapy. SSE1 may become a candidate for potential therapy against Shigella dysenteriae infection in clinical applications.

Plant organellar DNA polymerases are replicative and translesion DNA synthesis polymerases

Genomes acquire lesions that can block the replication fork and some lesions must be bypassed to allow survival. The nuclear genome of flowering plants encodes two family-A DNA polymerases (DNAPs), the result of a duplication event, that are the sole DNAPs in plant organelles. These DNAPs, dubbed Plant Organellar Polymerases (POPs), resemble the Klenow fragment of bacterial DNAP I and are not related to metazoan and fungal mitochondrial DNAPs. Herein we report that replicative POPs from the plant model Arabidopsis thaliana (AtPolI) efficiently bypass one the most insidious DNA lesions, an apurinic/apyrimidinic (AP) site. AtPolIs accomplish lesion bypass with high catalytic efficiency during nucleotide insertion and extension. Lesion bypass depends on two unique polymerization domain insertions evolutionarily unrelated to the insertions responsible for lesion bypass by DNAP θ, an analogous lesion bypass polymerase. AtPolIs exhibit an insertion fidelity that ranks between the fidelity of replicative and lesion bypass DNAPs, moderate 3′-5′ exonuclease activity and strong strand-displacement. AtPolIs are the first known example of a family-A DNAP evolved to function in both DNA replication and lesion bypass. The lesion bypass capabilities of POPs may be required to prevent replication fork collapse in plant organelles.