Distribution of transcription factor binding sites along 5'-upstream sequences of genes: estimation of minimal promoters and upstream regulatory regions
Precise analysis of gene transcription regulation requires accurate estimation of gene regulatory elements. Transcription factors (TF) binding sites are distributed unevenly along gene 5'-upstream sequences. The analysis of gene 5'-upstream sequences showed the presence of high-density regions of transcription factor binding sites (HDR). The first HDR adjacent to the transcription start point corresponds to a minimal promoter, and the 5'-end of I-HDR corresponds to the 5'-end of minimal promoter. The HDRs located more distant to gene transcription start point often correspond to enhancers and other gene regulatory elements. The commons for milk protein genes TF binding sites are located in I- and II-HDR suggesting that tissue- and time-specificity of this group of genes are determined by minimal promoter, enhancer or by both. The analysis of distribution of TF binding sites along gene 5'-upstream sequences suggested that the expression of rabbit a casein gene can be regulated by minimal promoter only. The expression of all analyzed WAP genes; bovine and goat k casein, bovine and goat BGL, and rabbit a lactalbumin genes are shown to be regulated by an enhancer. The expression of all b casein genes; bovine and rat a casein; goat, mice and rat a lactalbumin genes are found to be regulated by both regulatory elements.
Tadeusz Malewski, Department of Molecular Biology, Institute of Genetics and Animal Breeding, Polish Academy of Sciences, Jastrzebiec, 05-552, Wolka Kosowska, Poland