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5'-Flanking Regions of Camel Milk Genes Are Highly Similar to Homologue Regions of Other Species and Can be Divided into Two Distinct Groups

Laboratory of Dairy Science, Institute of Food Science, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland

Corresponding author:
S. R. Kappeler; e-mail:
stefan.kappeler{at}alumni.ethz.ch.

The concentrations of individual casein and whey proteins in camel milk differ markedly to respective protein concentrations in bovine milk. The ratio of ß-casein to -casein is considerably higher in camel milk. ß-Lactoglobulin is absent, but whey acidic protein and peptidoglycan recognition protein have been detected. Genomic sequences upstream to milk-protein genes, which are known to regulate the expression of milk proteins to a great extent, were determined for 10 camel milk-protein genes and compared to respective sequences in other mammals. Multiple sequence alignment showed closest relationships to homologous sequences from other mammals. Comparison of milk protein regulative regions revealed two distantly related groups with pronouncedly different transcription factor site probabilities. The GC-content in sequences of the first group was considerably higher than in sequences of the second group and combined occurrence of CAAT and TATAA boxes was rare, suggesting that the first group represented mostly the housekeeping gene type, probably regulated by cellular signal transduction pathways, whereas the second group helped to regulate genes specifically expressed in terminally differentiated cells of the lactating alveolar epithelium. A core region of the composite response element, which primarily controls milk protein gene activity, was found by a search for elements conserved within all 5'-flanking sequences analyzed, and it is assumed, that the presence of this element determines gene expression in the lactating mammary gland, and binding sites for general activator and repressor factors, surrounding the milk protein gene specific element, are important for regulation of gene activity.

Key Words: camel • gene expression • milk protein • transcription factor binding site

Abbreviation key: 5'-flanking region = gene sequence 5'-flanking to the transcriptional start site of the milk-protein genes examined, TF = transcription factor. Abbreviations for transcription factors follow the TRANSFAC entries ( Wingender et al. 2000)

This article has been cited by other articles:

				S. R. Kappeler, C. Heuberger, Z. Farah, and Z. Puhan Expression of the Peptidoglycan Recognition Protein, PGRP, in the Lactating Mammary Gland J Dairy Sci, August 1, 2004; 87(8): 2660 - 2668. [Abstract] [Full Text] [PDF]