[Sequence characterization of the 5'-Flanking region of the GHR gene in Tibetan sheep]

Abstract

The 5'-Flanking sequence (including the P1 promotor and exon 1A) of the GHR gene in Oura-type Tibetan sheep (O. aries) was cloned by T-A method and sequenced (GenBank accession No. EF116490). Characterization and comparison of this sequence with mouflons (O. musimon), goat (C. hircus), cattle (B. taurus) and European bison (B. bonasus) orthologues were also conducted. Results showed that: 1) The 5'-flanking region contained many potential transcriptional factor binding sites such as those for C/EBPb, C/EBP, SP1, Cap, USF, HFH-2, HNF-3b, and Oct-1, which might have an important effect on transcription activation and regulation as well as tissue-specific expression. The rate of repetitive sequences was 2.55% and no SINEs, LINEs, LTR anti-transcription elements or DNA transposon elements were found, although one (TG)11 microsatellite was found. 2) In the P1 promotor region, sequence homology between the Tibetan sheep and mouflon, goat, cattle and European bison was 99.7%, 94.2%, 85.9% and 86.5%, respectively, while that for exon 1A was 99.0%, 97.0%, 92.7% and 94.6%, respectively. 3) The molecular phylogenetic tree among these species, constructed by the neighborhood joining method based on the sequences of no-coding region of the GHR genes, placed the two Bovinae species on one branch and the three Caprinae species on the other. Tibetan sheep and mouflons were joined first, followed by the goat, and then the Bovinae species, including the cattle and European bison. This result of phylogenetic clustering was not only identical to the taxonomy, but also to the phylogenetic clustering using the mitochondrial DNA of these species.