Regulation of poly(ADP-ribose) polymerase-1 (PARP-1) gene expression through the post-translational modification of Sp1: a nuclear target protein of PARP-1.
BACKGROUND
Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme that plays critical functions in many biological processes, including DNA repair and gene transcription. The main function of PARP-1 is to catalyze the transfer of ADP-ribose units from nicotinamide adenine dinucleotide (NAD+) to a large array of acceptor proteins, which comprises histones, transcription factors, as well as PARP-1 itself. We have previously demonstrated that transcription of the PARP-1 gene essentially rely on the opposite regulatory actions of two distinct transcription factors, Sp1 and NFI. In the present study, we examined whether suppression of PARP-1 expression in embryonic fibroblasts derived from PARP-1 knockout mice (PARP-1-/-) might alter the expression and/or DNA binding properties of Sp1 and NFI. We also explored the possibility that Sp1 or NFI (or both) may represent target proteins of PARP-1 activity.


RESULTS
Expression of both Sp1 and NFI was found to be considerably reduced in PARP-1-/- cells. Co-immunoprecipitation assays revealed that PARP-1 physically interacts with Sp1 in a DNA-independent manner, but neither with Sp3 nor NFI, in PARP-1+/+ cells. In addition, in vitro PARP assays indicated that PARP-1 could catalyze the addition of polymer of ADP-ribose to Sp1, which also translated into a reduction of Sp1 binding to its consensus DNA target site. Transfection of the PARP-1 promoter into both PARP-1+/+ and PARP-1-/- cells revealed that the lack of PARP-1 expression in PARP-1-/- cells also results in a strong increase in PARP-1 promoter activity. This influence of PARP-1 was found to rely on the presence of the Sp1 sites present on the basal PARP-1 promoter as their mutation entirely abolished the increased promoter activity observed in PARP-1-/- cells. Subjecting PARP-1+/+ cells to an oxidative challenge with hydrogen peroxide to increase PARP-1 activity translated into a dramatic reduction in the DNA binding properties of Sp1. However, its suppression by the inhibitor PJ34 improved DNA binding of Sp1 and led to a dramatic increase in PARP-1 promoter function.


CONCLUSIONS
Our results therefore recognized Sp1 as a target protein of PARP-1 activity, the addition of polymer of ADP-ribose to this transcription factor restricting its positive regulatory influence on gene transcription.
Zaniolo
Karine
K
Oncology and Molecular Endocrinology Research Center, Centre de Recherche du CHUL-CHUQ and Département d'Anatomie-Physiologie, Université Laval, Québec, G1V 4G2, Canada. Karine.zaniolo@crchul.ulaval.ca
Desnoyers
Serge
S
Leclerc
Steeve
S
Guérin
Sylvain L
SL
D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D000071137:Poly (ADP-Ribose) Polymerase-1; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D011506:Proteins / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000378:metabolism; D041701:Swiss 3T3 Cells
D011506:Proteins; D016329:Sp1 Transcription Factor; C024857:poly(ADP)-ribosylated proteins; D051705:Sp3 Transcription Factor; D011064:Poly Adenosine Diphosphate Ribose; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases