Open AccessThe orf 4 gene of the enterobacterial ICE, R391, encodes a novel UV‐inducible recombination directionality factor, Jef, involved in excision and transfer of the ICE
Author(s) -
O'Halloran John A.,
McGrath Barry M.,
Pembroke J. Tony
Publication year - 2007
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2007.00747.x
Subject(s) - biology , genetics , gene , homology (biology) , amplicon , nucleotide excision repair , horizontal gene transfer , mutant , microbiology and biotechnology , dna repair , polymerase chain reaction , phylogenetics
The enterobacterial mobile genetic element R391, the prototype ICE (integrating‐conjugative element) of the SXT/R391 family, shows increased conjugative transfer following UV irradiation. This is dependent on a functioning R391 orf 4 gene, which is adjacent to the element encoded integrase gene, int . orf 4 mutants fail to form a detectable circular transfer intermediate, do not show UV induced transfer and show a much reduced general transfer ability. The orf 4 gene product, termed Jef (IncJ excision factor), shows little homology to anything currently in the nucleotide or protein databases. It is predicted to encode a 66 amino acid, 8.03 kDa, basic, DNA‐binding protein with an iso‐electric point of pH 8.1: these characteristics being similar to those of recombinational directionality factors involved in excision. Jef expression is up‐regulated upon UV irradiation as demonstrated by real‐time reverse transcriptase PCR and is controlled by two element encoded genes orf 90 and orf 91, which show similarity to the transcriptional activator complex FlhC and FlhD . orf 4, orf 90 and orf 91 are conserved in all the SXT/R391‐like elements sequenced to date including SXT, ICE Spu PO1 and ICE Vch Mex1. orf 4 is also conserved in other SXT/R391 family members such as R997, R392, R705 and pMERPH as shown by sequencing amplicons from these ICEs generated using orf 4 specific primers.