The Acinetobacter regulatory UmuDAb protein cleaves in response to DNA damage with chimeric LexA/UmuD characteristics.
In the DNA damage response of most bacteria, UmuD forms part of the error-prone (UmuD'(2) )C polymerase V and is activated for this function by self-cleavage after DNA damage. However, the umuD homolog (umuDAb) present throughout the Acinetobacter genus encodes an extra N-terminal region, and in Acinetobacter baylyi, regulates transcription of DNA damage-induced genes. UmuDAb expressed in cells was correspondingly larger (24 kDa) than the Escherichia coli UmuD (15 kDa). DNA damage from mitomycin C or UV exposure caused UmuDAb cleavage in both E. coli wild-type and ΔumuD cells on a timescale resembling UmuD, but did not require UmuD. Like the self-cleaving serine proteases LexA and UmuD, UmuDAb required RecA for cleavage. This cleavage produced a UmuDAb' fragment of a size consistent with the predicted cleavage site of Ala83-Gly84. Site-directed mutations at Ala83 abolished cleavage, as did mutations at either the Ser119 or Lys156 predicted enzymatic residues. Co-expression of the cleavage site mutant and an enzymatic mutant did not allow cleavage, demonstrating a strictly intramolecular mechanism of cleavage that more closely resembles the LexA-type repressors than UmuD. These data show that UmuDAb undergoes a post-translational, LexA-like cleavage event after DNA damage, possibly to achieve its regulatory action.
Department of Biology and Chemistry, Morehead State University, KY, USA. jm.hare@moreheadstate.edu
Janelle M
JM
Hare
Sabal
S
Adhikari
Kasandra V
KV
Lambert
Alexander E
AE
Hare
Alison N
AN
Grice
D000150:Acinetobacter / Q000201:enzymology* / Q000235:genetics* / Q000528:radiation effects; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000528:radiation effects; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004259:DNA-Directed DNA Polymerase; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C055218:UmuD protein, E coli