Neutrophil lactoferrin upregulates the human p53 gene through induction of NF-kappaB activation cascade.
Neutrophil lactoferrin (Lf) was previously shown to act as a transcriptional activator in various mammalian cells. Here, we describe that Lf specifically transactivates the p53 tumor suppressor gene through the activation of nuclear factor-kappaB (NF-kappaB) and consequently regulates p53-responsive oncogenes. In HeLa cervical carcinoma cells stably expressing Lf (HeLa-Lf), expression of mdm2 and p21waf1/cip1 as well as p53 was greatly enhanced. Transient expression of Lf also markedly transactivates transcription of a p53 promoter-driven reporter and NF-kappaB-driven reporters in various mammalian cells. However, mutation of the NF-kappaB site or treatment with an NF-kappaB inhibitor abrogated the transactivation, suggesting that NF-kappaB should play an essential role in the Lf-induced transactivation. Increased binding activity and nuclear translocation of p65 in response to Lf strongly support these findings. Furthermore, Lf-mediated NF-kappaB activation is diminished in IKKalpha- or IKKbeta-deficient mouse embryonic fibroblast cells. The activation of both IKKs and NF-kappaB by Lf is over-ridden by the expression of dominant-negative mutants of NIK, MEKK1, IKKalpha and IKKbeta. Collectively, we conclude that overexpressed Lf directly relays signals to upstream components responsible for NF-kappaB activation, thereby leading to the activation of NF-kappaB target genes.
Oh
Sang-Muk
SM
School of Life Sciences and Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-gu, Seoul 136-701, Korea.
Pyo
Chul-Woong
CW
Kim
Youngho
Y
Choi
Sang-Yun
SY
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D016158:Genes, p53; D006801:Humans; D007781:Lactoferrin / Q000502:physiology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
D017931:DNA Primers; D016328:NF-kappa B; D007781:Lactoferrin