The Osgin gene family consists of two members, Osgin1 and Osgin2, involved in the cellular oxidative stress response. While many members of this essential cellular pathway have been extensively characterized, the Osgin gene family, despite its broad phylogenetic distribution, has received far less attention. Here, we review published articles and open-source databases to synthesize the current research on the evolutionary history, structure, biochemical and physiological functions, expression patterns, and role in disease of the Osgin gene family. Although Osgin displays broad spatiotemporal expression during development and adulthood, there is ambiguity regarding the cellular functions of the OSGIN proteins. A recent study identified OSGIN-1 as a flavin-dependent monooxygenase, but the biochemical role of OSGIN-2 has not yet been defined. Moreover, while the Osgin genes are implicated as mediators of cell proliferation, apoptosis, and autophagy, these functions have not been connected to the enzymatic classification of OSGIN. Misregulation of Osgin expression has long been associated with various disease states, yet recent analyses highlight the mechanistic role of OSGIN in pathogenesis and disease progression, underscoring the therapeutic potential of targeting OSGIN. In light of these findings, we suggest further avenues of research to advance our understanding of this essential, yet underexplored, gene family.

Phage satellites are mobile genetic elements that parasitize a helper phage to complete their life cycle. While phage satellites are widespread in diverse bacterial hosts, none have yet been isolated in Mycobacteriaceae. Here, we report the first phage satellites isolated and characterized in Mycobacteriaceae, Extracellular Prophage-Inducing Particles (EPIPs). EPIPs induce a helper phage-HerbertWM, a Mycolicibacterium aichiense prophage-upon infection. Genomic sequencing of thirteen isolates revealed a genome size of ∼11 kb and ∼83.3% nucleotide similarity calculated using Virus Intergenomic Distance Calculator (VIRIDIC). Although gene content and synteny were broadly conserved across the isolates, the EPIPs were categorized into distinct groups based on VIRIDIC similarity scores, gene content, and synteny. Notably, EPIPs lack capsid proteins, tail proteins, and holins, suggesting EPIPs hijack the machinery of HerbertWM to replicate, assemble, and lyse the host. Furthermore, the unique gene content of EPIPs compared to other phage satellites, particularly the presence of a tape measure protein and absence of antirepressors, suggests they are distinct from other phage satellite classes. Transmission electron microscopy of EPIPs reveals that they not only feature smaller capsids compared to HerbertWM, but that they feature highly flexible tails of variable length. Additionally, greater EPIP protein similarity to proteins in bacteria as opposed to free phage proteins suggests a functional or evolutionary relationship may exist. The nucleotide similarity, synteny, and unique gene content of EPIPs suggest EPIPs are a distinct class of phage satellites that induce Mycobacteriaceae prophages.