title: Regulation of the poly(ADP-ribose) polymerase-1 gene expression by the transcription factors Sp1 and Sp3 is under the influence of cell density in primary cultured cells.
abstract: PARP-1 [poly(ADP-ribose) polymerase-1) is a nuclear enzyme that is involved in several cellular functions, including DNA repair, DNA transcription, carcinogenesis and apoptosis. The activity directed by the PARP-1 gene promoter is mainly dictated through its recognition by the transcription factors Sp1 and Sp3 (where Sp is specificity protein). In the present study, we investigated whether (i) both PARP-1 expression and PARP-1 enzymatic activity are under the influence of cell density in primary cultured cells, and (ii) whether its pattern of expression is co-ordinated with that of Sp1/Sp3 at varying cell densities and upon cell passages. All types of cultured cells expressed PARP-1 in Western blot when grown to sub-confluence. However, a dramatic reduction was observed at post-confluence. Similarly, high levels of Sp1/Sp3 were observed by both Western blot and EMSAs (electrophoretic mobility-shift assays) in sub-confluent,but not post-confluent, cells. Consistent with these results, the promoter of the rPARP-1 (rat PARP-1) gene directed high levels of activity in sub-confluent, but not confluent, cells upon transfection of various CAT (chloramphenicol acetyltransferase)-rPARP-1 promoter constructs into cultured cells. The positive regulatory influence of Sp1 was not solely exerted on the rPARP-1 promoter constructs, as inhibition of endogenous Sp1 expression in HDKs(human dermal keratinocytes) through the transfection of Sp1 RNAi (RNA interference) considerably reduced endogenous hPARP-1 (human PARP-1) expression as well. The reduction in PARP-1 protein expression as cells reached confluence also translated into a corresponding reduction in PARP-1 activity. In addition, expression of both Sp1/Sp3, as well as that of PARP-1,was dramatically reduced as cells were passaged in culture and progressed towards irreversible terminal differentiation. PARP-1 gene expression therefore appears to be co-ordinated with that of Sp1 and Sp3 in primary cultured cells, suggesting that PARP-1 may play some important functions during the proliferative burst that characterizes wound healing.
authors.affiliation: Oncology and Molecular Endocrinology Research Center, CHUL Research Center, Centre Hospitalier Universitaire de Québec and Laval University, Sainte-Foy, Québec, G1V 4G2, Canada.
authors.forename: Karine
authors.initials: K
authors.lastname: Zaniolo
authors.forename: Anne
authors.initials: A
authors.lastname: Rufiange
authors.forename: Steeve
authors.initials: S
authors.lastname: Leclerc
authors.forename: Serge
authors.initials: S
authors.lastname: Desnoyers
authors.forename: Sylvain L
authors.initials: SL
authors.lastname: Guérin
mesh_terms: D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation; D002478:Cells, Cultured; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011817:Rabbits; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor; D011065:Poly(ADP-ribose) Polymerases