Differential gene expression activity among species-specific polypyrimidine/polypurine motifs in mu opioid receptor gene promoters.
The mu opioid receptor (MOR) is the principle molecular target of opioid analgesics. An appropriate understanding of MOR gene expression across species is critical for understanding its analgesic functions in humans. Here, we undertake a cross-species analysis of the polymorphic polypyrimidine/polypurine (PPy/u) motif, a key enhancer of MOR gene expression. The mouse PPy/u motif is highly homologous to those of rat (67%) and human (83%), but drives reporter gene expression tenfold and fivefold more effectively than those of rat and human, respectively. Circular dichroism profiles of PPy/u oligonucleotides from different species showed that they are primarily different in structure. Conformational studies of reporter plasmids using confocal Raman spectra, S1 nuclease and restriction enzymes demonstrated that the structural difference is the result of changes in the phosphodiester backbone. Furthermore, these conformational disparities produce differences in torsional stress, as shown by topoisomerase II relaxation and activation of different levels of gene expression under hypertonic conditions. This study demonstrates that homologous PPy/u motifs adopt unique species-specific conformations with different mechanisms and activities for gene expression. We further discuss how structural aspects of transcription regulatory elements, rather than the sequence itself, are significant when studying functional gene expression regulatory elements.
Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA. chungychoe@gmail.com
Chung-Youl
CY
Choe
Jinping
J
Dong
Ping-Yee
PY
Law
Horace H
HH
Loh
D000818:Animals; D001483:Base Sequence; D002942:Circular Dichroism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D051381:Rats; D017450:Receptors, Opioid, mu / Q000235:genetics*; D015183:Restriction Mapping / Q000379:methods; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D017450:Receptors, Opioid, mu