Functional characterisation of the bovine neuropeptide Y gene promoter and evaluation of the transcriptional activities of promoter haplotypes.

Neuropeptide Y (NPY) is a potent orexigenic agent. The molecular mechanisms underlying the regulation of bovine NPY gene expression by its promoter region is currently unknown. The objectives of this research were to: (i) identify the SNPs in the promoter region of the bovine NPY gene, (ii) investigate the effects of these SNPs by measuring promoter transcriptional activities of different bovine NPY promoter haplotypes and; (iii) identify the minimal promoter region (MPR) required for basal activity of the NPY gene in vitro. Seventeen SNPs were identified in the promoter region. Of these, 14 affected putative transcription factors binding motifs including a TATA binding protein factor at -20, GC-Box factors SP1 at -170 and GATA binding motifs at -120 and -347. The SNPs were assigned to five major haplotypes (BtNPY_H1-5), of which BtNPY_H5 had maximum transcriptional activity. The region extending to -134 nt was identified as the MPR. This MPR was confirmed by the identification of a putative TATA box (-29 nt) and two SP1/GC binding sites (-94 and -118 nt), within this region. However, promoter expression was significantly enhanced when the construct contained the -614 to -1019 nt region. In conclusion, a number of SNPs characterised in the bovine NPY promoter especially those affecting the transcription factor binding sites, enhancer and repressor regions have the potential to affect NPY gene expression. Natural variation exists in the promoter region of the bovine NPY gene, which should be further explored for selection of energetic efficiency in cattle.