Breast milk lactoferrin regulates gene expression by binding bacterial DNA CpG motifs but not genomic DNA promoters in model intestinal cells.
High-affinity binding of DNA by lactoferrin (LF) is an established phenomenon, but the biologic function of this interaction remains unclear. LF is an abundant breast milk protein (12.5-87.5 micromol/L) and is resistant to digestion in the infant gut. Regulation of gene expression by LF appears to be a major activity, particularly in modulating immune responses. We hypothesized that LF binding to DNA is a mechanism of gene regulation and aimed to identify the mechanism and physiologic sites of this activity. Our studies focused on two major biologic compartments of DNA: LF binding to proinflammatory bacterial DNA sequences (CpG motifs) in extracellular compartments and LF binding to genomic DNA promoters in the nucleus. LF 0.5 mmol/L inhibited CpG motif-induced nuclear factor-kappaB (NF-kappaB) activation and interleukin (IL)-8 and IL-12 cytokine gene transcription in B cells. Intestinal epithelial cells were unresponsive to CpG motifs. However, significant LF transferred across M cell-like monolayers, specialized epithelial cells that transcytose intact macromolecules to underlying B-cell follicles in the intestine. LF did not activate gene expression by binding to putative response elements in epithelial and lymphoid cells. Nor did LF bind to putative response elements specifically in gel-shift assays. No nuclear localization of LF was detected in green fluorescent protein (GFP) tagging experiments. We conclude that breast milk LF regulates gene expression by binding CpG motifs extracellularly, with follicular B cells in the infant intestine a likely target.
Mulligan
Peter
P
Adult and Paediatric Gastroenterology, Institute of Cell and Molecular Science, Barts and The London, Queen Mary's School of Medicine and Dentistry, London E1 2AD, United Kingdom.
White
Nicholas R J
NR
Monteleone
Giovanni
G
Wang
Ping
P
Wilson
James W
JW
Ohtsuka
Yoshi
Y
Sanderson
Ian R
IR
D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D016207:Cytokines / Q000235:genetics; D004247:DNA / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D007781:Lactoferrin; D008895:Milk, Human / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*; D011401:Promoter Regions, Genetic
C408982:CPG-oligonucleotide; D002352:Carrier Proteins; D016207:Cytokines; C490098:LTF protein, human; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D004247:DNA; D007781:Lactoferrin