PMID:22227494

Citation	Savinov, A, Pan, J, Ghosh, P and Hatfull, GF (2012) The Bxb1 gp47 recombination directionality factor is required not only for prophage excision, but also for phage DNA replication. Gene 495:42-8
Abstract	Mycobacteriophage Bxb1 encodes a serine-integrase that catalyzes both integrative and excisive site-specific recombination. However, excision requires a second phage-encoded protein, gp47, which serves as a recombination directionality factor (RDF). The viability of a Bxb1 mutant containing an S153A substitution in gp47 that eliminates the RDF activity of Bxb1 gp47 shows that excision is not required for Bxb1 lytic growth. However, the inability to construct a Δ47 deletion mutant of Bxb1 suggests that gp47 provides a second function that is required for lytic growth, although the possibility of an essential cis-acting site cannot be excluded. Characterization of a mutant prophage of mycobacteriophage L5 in which gene 54 - a homologue of Bxb1 gene 47 - is deleted shows that it also is defective in induced lytic growth, and exhibits a strong defect in DNA replication. Bxb1 gp47 and its relatives are also unusual in containing conserved motifs associated with a phosphoesterase function, although we have not been able to show robust phosphoesterase activity of the proteins, and amino acid substitutions with the conserved motifs do not interfere with RDF activity. We therefore propose that Bxb1 gp47 and its relatives provide an important function in phage DNA replication that has been co-opted by the integration machinery of the serine-integrases to control the directionality of recombination.
Links	PubMed PMC3273658 Online version:10.1016/j.gene.2011.12.003
Keywords	Amino Acid Sequence; Base Sequence; DNA Replication/genetics; Integrases/genetics; Integrases/physiology; Molecular Sequence Data; Mycobacteriophages/enzymology; Mycobacteriophages/genetics; Recombination, Genetic; Sequence Deletion; Virus Activation/genetics; Virus Replication/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPML5:VG54		GO:0006260: DNA replication	IMP: Inferred from Mutant Phenotype:	P	Figure 4 shows that GP 54 causes an increase in the amount of DNA following induction. GP 54 is being compared to a mutant of itself that does not perform the same the function.	complete

References

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