Functional polymorphism and differential regulation of CYSLTR1 transcription in human airway smooth muscle and monocytes

Abstract

Cysteinyl leukotrienes play an important role in the pathophysiology of many inflammatory disorders,

including asthma. The aim of this study was to characterize the mechanisms underlying transcriptional regula- tion of the human cysteinyl leukotriene receptor 1 (hCYSLTR1) gene. 5’RACE was performed on human airway

smooth muscle (HASM) and peripheral blood mononuclear cells. A 1128-bp region of the hCYSLTR1 main puta- tive promoter was screened for polymorphisms by sequencing of 48 individuals. Luciferase reporter gene assays

were performed using fragments of the core promoter (232 bp to 1128 bp) in HASM and THP1 cells. Three hCYSLTR1 transcripts were found, one representing 90% of all messenger RNA identified. The genomic location

of the transcription start sites suggested there are two putative hCYSLTR1 promoters. The majority of the tran- scriptional activity of the main putative promoter was detected between –232 and –679 bp. Four single- nucleotide polymorphisms in strong linkage disequilibrium were found in the region studied: –561 (rs7066737),

–642 (rs2806489), –781 (rs2637204), and –940 (rs321029), with three haplotypes observed. In THP1 cells, the G allele (–642) caused a twofold decrease in luciferase expression compared to the A allele. These data suggest that

the majority of hCYSLTR1 transcripts in HASM and monocytes arise from a single promoter located immedi- ately upstream of the 5’ untranslated region, although rarer transcripts can also occur. This study also raises the

possibility that cell-type-dependent differences in transcriptional activity caused by the presence of specific hap- lotypes within the main CYSLTR1 promoter may be a predictor of disease risk or treatment response.