title: Gene 5.5 protein of bacteriophage T7 in complex with Escherichia coli nucleoid protein H-NS and transfer RNA masks transfer RNA priming in T7 DNA replication.
abstract: DNA primases provide oligoribonucleotides for DNA polymerase to initiate lagging strand synthesis. A deficiency in the primase of bacteriophage T7 to synthesize primers can be overcome by genetic alterations that decrease the expression of T7 gene 5.5, suggesting an alternative mechanism to prime DNA synthesis. The product of gene 5.5 (gp5.5) forms a stable complex with the Escherichia coli histone-like protein H-NS and transfer RNAs (tRNAs). The 3'-terminal sequence (5'-ACCA-3') of tRNAs is identical to that of a functional primer synthesized by T7 primase. Mutations in T7 that suppress the inability of primase reduce the amount of gp5.5 and thus increase the pool of tRNA to serve as primers. Alterations in T7 gene 3 facilitate tRNA priming by reducing its endonuclease activity that cleaves at the tRNA-DNA junction. The tRNA bound to gp5.5 recruits H-NS. H-NS alone inhibits reactions involved in DNA replication, but the binding to gp5.5-tRNA complex abolishes this inhibition.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA. Bin_Zhu@hms.harvard.edu
authors.forename: Bin
authors.initials: B
authors.lastname: Zhu
authors.forename: Seung-Joo
authors.initials: SJ
authors.lastname: Lee
authors.forename: Min
authors.initials: M
authors.lastname: Tan
authors.forename: En-Duo
authors.initials: ED
authors.lastname: Wang
authors.forename: Charles C
authors.initials: CC
authors.lastname: Richardson
mesh_terms: D017123:Bacteriophage T7 / Q000235:genetics*; D004265:DNA Helicases / Q000378:metabolism; D019915:DNA Primase / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000821:virology; D029968:Escherichia coli Proteins / Q000235:genetics*; D036781:Fimbriae Proteins / Q000235:genetics*; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D010957:Plasmids / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D017931:DNA Primers; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; D014764:Viral Proteins; C080078:gene 5.5 protein, Bacteriophage T7; D036781:Fimbriae Proteins; D012343:RNA, Transfer; D019915:DNA Primase; D004720:Endonucleases; D004265:DNA Helicases