Characterization and functional analysis of the porcine lactoferrin gene promoter

Estrogen and glucocorticoid promote the lactoferrin synthesis and secretion ability of bovine mammary epithelial cells through ER and GR signaling pathways

Lactoferrin (LF) is an innate immunity glycoprotein with antibacterial, anti-inflammatory, antiviral, anti-tumor, and autoantibody activity-enhancing properties. Steroid hormones are essential for development and lactation in the dairy cow mammary gland, and act through binding to receptors that drive gene transcription. However, it remains unclear whether steroid hormone receptors play roles in LF synthesis in bovine mammary epithelial cells (BMECs). In this study, we investigated the direct effects of estrogen and glucocorticoid on LF synthesis and secretion by BMECs. The results show that treatment of BMECs with estrogen (17-β-estradiol, E2) and glucocorticoid (hydrocortisone) significantly promoted cell proliferation. Furthermore, E2 or hydrocortisone increased the expression levels of estrogen receptor (ER) and glucocorticoid receptor (GR), and stimulated the synthesis and secretion of LF in BMECs. Treatment of BMECs with various inhibitors (fulvestrant, mifepristone, and pimozide) decreased LF gene transcript and LF protein levels. It was concluded that fulvestrant and mifepristone inhibit LF transcription and translation via inhibiting ER and GR, respectively. Our data indicate that E2 and hydrocortisone regulate LF protein synthesis through the ER and GR signaling pathways. These results provide new information about the regulation of the synthesis of functional proteins in milk.

Bovine lactoferrin (LTF) gene promoter haplotypes have different basal transcriptional activities

Genetic polymorphisms present in the bovine lactoferrin (LTF) gene promoter have the potential to affect milk lactoferrin concentrations. The objectives were: (1) to identify, in silico, SNPs in the promoter region of the LTF gene that could affect transcription factor binding activity, (2) to investigate the effects of these SNPs in vitro by measuring promoter transcriptional activities of different bovine LTF promoter haplotypes and (3) to investigate the genetic association between LTF promoter SNPs and milk lactoferrin concentration. Haplotypes were deduced from sequencing of the 2.2-kb bovine LTF promoter in 78 unrelated animals. In silico analysis of the 2.2-kb promoter revealed two major haplotypes (BtLTF_H1a and BtLTF_H2a) that differed at 10 SNP loci that affect transcription factors of both a constitutive (at -28, -1702) and an inducible (at -131, -270, -586, -2047, -2077, -2122, -2140 and -2151) nature. The basal promoter transcriptional activity of BtLTF_H1a was 1.44-fold higher than that of BtLTF_H2a in mammary epithelial cells. Cows with the BtLTF_H1a haplotype had increased lactoferrin protein concentration in milk at various time points over the lactation curves, compared to herdmates with the BtLTF_H2a haplotype. The SNPs c.-28A>C, c.-131T>C, c.-156A>G, c.-270T>C, c.-586C>T, c.-1702A>G, c.-1953G>A, c.-2047A>G, c.-2077A>G, c.-2122C>T, c.-2140A>G and c.-2151G>A were associated (P < 0.001) with milk lactoferrin content in 372 Holstein-Friesian cows. The identification of bovine LTF promoter haplotypes with different basal transcriptional activities in vitro that are associated with lactoferrin levels in milk in vivo may facilitate the identification of designer dairy herds for increased lactoferrin content in milk.

Molecular cloning, promoter analysis and SNP identification of Italian Nicastrese and Saanen lactoferrin gene

Lactoferrin (Lf) is an iron-binding glycoprotein found in exocrine secretions including milk. High levels of lactoferrin may have a role in the prevention of microbial infection of the mammary gland. In this report we sequenced and characterized goat lactoferrin cDNA and its promoter region in two different breeds of goat. The complete cDNA comprised 2356 nucleotides, including 38 bp at the 5'-UTR and 194 bp at the 3'-UTR. The open reading frame is 2127 bp long and it encodes a mature protein of 689 aminoacids. A total of 19 nucleotide differences, 11 of them being responsible for 8 aminoacid changes, were identified through the comparison with French, Korean and Tibetan goat lactoferrin cDNAs. About 1700 bp of the lactoferrin gene promoter were sequenced. Sequence analysis revealed a non-canonical TATA box, multiple SP1/GC elements, and other putative binding sites for transcription factors, such as NF-kappaB, STAT3 and AP2. Two SNPs were identified, one of which would seem to create a new putative AP2 consensus sequence. The presence of an additional AP2 binding site could be associated with quantitative differences of such protein fraction, which could enhance all the activities related to such protein, and improve mammary gland defence against bacterial infections.

Characterization of the infection-responsive bovine lactoferrin promoter

The concentration of lactoferrin in bovine milk is dramatically increased in response to infection. The high levels of lactoferrin may have a role in the prevention of microbial infection of the mammary gland. However, molecular mechanisms of how the lactoferrin gene is regulated in the mammary gland in response to infection remain unknown. In this study, we isolated and characterized the 5' flanking region of the bovine lactoferrin gene. An 8.2 kilobase (kb) fragment of the bovine lactoferrin gene, containing 4.4 kb of 5' flanking region, exon 1, intron 1, and exon 2, was isolated from a bovine genomic library on two overlapping bacterial artificial chromosome (BAC) clones. Sequence analysis of the isolated lactoferrin gene revealed that the promoter region contains a high GC content, a non-canonical TATA box, multiple stimulating protein 1 (SP1)/GC elements, and other putative binding sites for transcription factors including nuclear factor-kappaB (NF-kappaB), activator protein 1 (AP1), signal transducer and activator of transcriptions 3 and 5 (STAT3 and STAT5), and steroid hormone receptors. To demonstrate that the isolated promoter is functional, 4.4 kb of 5' flanking region was inserted upstream from the firefly luciferase gene and the chimeric construct was transiently transfected into murine mammary epithelial cells. Transfection studies showed that the basal promoter activity is quite potent, being similar in strength to that of the simian virus 40 (SV40) promoter/enhancer. In addition, a 24-h treatment with Escherichia coli lipopolysaccharide (LPS) significantly stimulated its activity up to 2.3-fold in a dose-dependent manner. Furthermore, promoter deletion analysis indicated that the sequence up to -543 was sufficient for basal activity, whereas the sequence up to -1029 was required for maximal basal activity. The basal activity of the promoter is affected by both positive regulatory regions (-2462/-1879 and -1029/-75) and a negative regulatory region (-1407/-1029). LPS-responsive regions of the promoter were localized to the region from -1029 to -543 containing one STAT3 site and two NF-kappaB sites, and the region from -4355 to -2462 containing three AP1 sites and six NF-kappaB sites. Taken together, our findings suggested that the lactoferrin promoter responds to infection via the NF-kappaB pathway.

Lactoferrin gene expression and regulation: an overview

Lactoferrin is highly conserved among human, mouse, bovine, and porcine species. The numbers of amino acids encoded by 15 of the 17 exons in these species are identical, and in 12 locations, they have identical codon interruptions at the intron-exon splice junctions. However, lactoferrin expression is both ubiquitous and species, tissue, and cell-type specific. It is differentially regulated through multiple signaling pathways such as steroid hormone, growth factor, and kinase cascade pathways. Comparing the lactoferrin gene promoters from different species, common and different characteristics are observed. The human, mouse, bovine, porcine, and bubaline (African antelope) promoters all contain a noncanonical TATA box with an adjacent Sp1 site. Both human and mouse have multiple steroid hormone response elements, while none are found in the other species studied, suggesting that the lactoferrin gene is differentially regulated among different species by steroid hormones. Several transcription factors have been identified that are crucial for the expression of the lactoferrin gene during differentiation of the myeloid cells and in estrogen and epidermal growth factor regulation. This article provides an overview on lactoferrin expression and regulation in different species.

Molecular cloning and sequence analysis of bubaline lactoferrin promoter

The proximal promoter for bubaline lactoferin-encoding gene has been isolated, cloned and sequenced. A 468 bp fragment of the 5' flanking region of the lactoferrin gene was PCR amplified and cloned into pUC18 vector. Sequence analysis of the amplified fragment revealed the presence of one TATA box, one TATA like element, two GC boxes and one motif resembling cAMP response element (CRE) in this region. Bubaline lactoferrin promoter shares 93%, 53%, 52% and 48% homology with cattle, pig, mouse and human lactoferrin 5' flanking region, respectively.