TY - JOUR
T1 - Transfection enhancement in Bacillus subtilis displays features of a novel DNA repair pathway II
T2 - host constitutive expression, repair DNA synthesis, and in vitro activity
AU - Radany, Eric H.
AU - Malanoski, Gregory
AU - Ambulos, Nicholas P.
AU - Friedberg, Errol C.
AU - Yasbin, Ronald E.
N1 - Funding Information:
We thank the several investigators noted for gifts of strains and materials, and Kenneth Dornfeld for thoughtful comments on the draft manuscript. This work was supported in part by grants from the NIH (1 K08-CA-1590) to E.H.R., and the National Science Foundation (MCB-9219436) to R.E.Y.
PY - 1997/8
Y1 - 1997/8
N2 - In the Bacillus subtilis genetic system, transfection refers to uptake of isolated bacteriophage DNA by competent host cells, sometimes followed by productive cell infection. Previous studies have shown that ultraviolet (UV)-irradiation of the competent host cells, or cotransfection of UV-irradiated heterologous DNA, can increase the efficiency of transfection in some cases; these latter two phenomena have been called transfection enhancement (TE). In an accompanying paper, we show that the TE is apparently confined to the B. subtilis phages that contain hydroxymethyluracil (HMU) in their DNA, and that the photoproduct in UV-irradiated DNA that mediates TE is specific, and differerent than the pyrimidine dimer, thymine glycol, uracil, or HMU. We also show that TE is due to reduced intracellular endonucleolytic attack of transfecting DNA. Based on this DNA base and nucleolytic specificity, we hypothesized that TE reflects the incidental action of a host DNA repair system on transfecting HMU phage DNA. In continuing these studies, we show here that duplex infecting HMU phage DNA is apparently inactivated by this same putative repair system when phage protein synthesis is blocked. We find, too, that this inactivation of infecting HMU phage DNA can be inhibited by UV-irradiated DNA, and that this process has a similar DNA base specificity as for TE. The survival of infecting HMU phage DNA is dependent on host DNA polymerase activity. We can detect specific DNA synthesis consist with formation of repair patches when inactivation of infecting HMU phase DNA is ongoing, but not when it is inhibited by the presence of UV DNA or by allowing phage gene expression. Each of these results is consistent with the hypothesis that TE reflects the action of a novel DNA repair pathway. We show that a candidate TE-associated enzymatic activity can be detected in cell free extracts of uninfected, but not HMU phage-infected B. subtilis cells. Correspondingly, the extracts of phage-infected cells appear to contain a diffusible factor that acts as an inhibitor of this host enzyme.
AB - In the Bacillus subtilis genetic system, transfection refers to uptake of isolated bacteriophage DNA by competent host cells, sometimes followed by productive cell infection. Previous studies have shown that ultraviolet (UV)-irradiation of the competent host cells, or cotransfection of UV-irradiated heterologous DNA, can increase the efficiency of transfection in some cases; these latter two phenomena have been called transfection enhancement (TE). In an accompanying paper, we show that the TE is apparently confined to the B. subtilis phages that contain hydroxymethyluracil (HMU) in their DNA, and that the photoproduct in UV-irradiated DNA that mediates TE is specific, and differerent than the pyrimidine dimer, thymine glycol, uracil, or HMU. We also show that TE is due to reduced intracellular endonucleolytic attack of transfecting DNA. Based on this DNA base and nucleolytic specificity, we hypothesized that TE reflects the incidental action of a host DNA repair system on transfecting HMU phage DNA. In continuing these studies, we show here that duplex infecting HMU phage DNA is apparently inactivated by this same putative repair system when phage protein synthesis is blocked. We find, too, that this inactivation of infecting HMU phage DNA can be inhibited by UV-irradiated DNA, and that this process has a similar DNA base specificity as for TE. The survival of infecting HMU phage DNA is dependent on host DNA polymerase activity. We can detect specific DNA synthesis consist with formation of repair patches when inactivation of infecting HMU phase DNA is ongoing, but not when it is inhibited by the presence of UV DNA or by allowing phage gene expression. Each of these results is consistent with the hypothesis that TE reflects the action of a novel DNA repair pathway. We show that a candidate TE-associated enzymatic activity can be detected in cell free extracts of uninfected, but not HMU phage-infected B. subtilis cells. Correspondingly, the extracts of phage-infected cells appear to contain a diffusible factor that acts as an inhibitor of this host enzyme.
KW - Bacillus subtilis
KW - DNA repair
KW - Transfection enhancement
KW - UV irradiation
UR - http://www.scopus.com/inward/record.url?scp=0030818632&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030818632&partnerID=8YFLogxK
U2 - 10.1016/S0921-8777(97)00018-9
DO - 10.1016/S0921-8777(97)00018-9
M3 - Article
C2 - 9298120
AN - SCOPUS:0030818632
SN - 0921-8777
VL - 384
SP - 121
EP - 134
JO - Mutation Research - DNA Repair
JF - Mutation Research - DNA Repair
IS - 2
ER -