title: Phage T4 SegB protein is a homing endonuclease required for the preferred inheritance of T4 tRNA gene region occurring in co-infection with a related phage.
abstract: Homing endonucleases initiate nonreciprocal transfer of DNA segments containing their own genes and the flanking sequences by cleaving the recipient DNA. Bacteriophage T4 segB gene, which is located in a cluster of tRNA genes, encodes a protein of unknown function, homologous to homing endonucleases of the GIY-YIG family. We demonstrate that SegB protein is a site-specific endonuclease, which produces mostly 3' 2-nt protruding ends at its DNA cleavage site. Analysis of SegB cleavage sites suggests that SegB recognizes a 27-bp sequence. It contains 11-bp conserved sequence, which corresponds to a conserved motif of tRNA TpsiC stem-loop, whereas the remainder of the recognition site is rather degenerate. T4-related phages T2L, RB1 and RB3 contain tRNA gene regions that are homologous to that of phage T4 but lack segB gene and several tRNA genes. In co-infections of phages T4 and T2L, segB gene is inherited with nearly 100% of efficiency. The preferred inheritance depends absolutely on the segB gene integrity and is accompanied by the loss of the T2L tRNA gene region markers. We suggest that SegB is a homing endonuclease that functions to ensure spreading of its own gene and the surrounding tRNA genes among T4-related phages.
authors.affiliation: Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Nauki ave., 5, Pushchino, Moscow, Russia.
authors.forename: Vera S
authors.initials: VS
authors.lastname: Brok-Volchanskaya
authors.forename: Farid A
authors.initials: FA
authors.lastname: Kadyrov
authors.forename: Dmitry E
authors.initials: DE
authors.lastname: Sivogrivov
authors.forename: Peter M
authors.initials: PM
authors.lastname: Kolosov
authors.forename: Andrey S
authors.initials: AS
authors.lastname: Sokolov
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlyapnikov
authors.forename: Valentine M
authors.initials: VM
authors.lastname: Kryukov
authors.forename: Igor E
authors.initials: IE
authors.lastname: Granovsky
mesh_terms: D017122:Bacteriophage T4 / Q000201:enzymology* / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D004279:DNA, Viral / Q000737:chemistry / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D005785:Gene Conversion; D040582:Inheritance Patterns; D017900:Myoviridae / Q000235:genetics; D016366:Open Reading Frames; D012343:RNA, Transfer / Q000235:genetics*; D013379:Substrate Specificity; D013604:T-Phages / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D012343:RNA, Transfer; D004706:Endodeoxyribonucleases