Authors: Raghu Prasad Rao Metpally Ramakrishnan Vigneshwar Ramanathan Sowdhamini
Publish Date: 2007/04/13
Volume: 32, Issue: 1, Pages: 43-50
Abstract
Nuclear hormone receptors NRs form a large superfamily of ligandactivated transcription factors which regulate genes underlying a wide range of patho physiological phenomena Availability of the full genome sequence of Tetraodon nigroviridis facilitated a genome wide analysis of the NRs in fish genome Seventy one NRs were found in Tetraodon and were compared with mammalian and fish NR family members In general there is a higher representation of NRs in fish genomes compared to mammalian ones They showed high diversity across classes as observed by phylogenetic analysis Nucleotide substitution rates show strong negative selection among fish NRs except for pregnane X receptor PXR estrogen receptor ER and liver X receptor LXR This may be attributed to crucial role played by them in metabolism and detoxification of xenobiotic and endobiotic compounds and might have resulted in slight positive selection Chromosomal mapping and pairwise comparisons of NR distribution in Tetraodon and humans led to the identification of nine synthenic NR regions of which three are common among fully sequenced vertebrate genomes Gene structure analysis shows strong conservation of exon structures among orthologoues Whereas paralogous members show different splicing patterns with intron gain or loss and addition or substitution of exons played a major role in evolution of NR superfamily
Keywords: