Department of Microbiology, Montana State University, Bozeman, Montana, United States of America.
PLoS One. 2011;6(12):e28712. doi: 10.1371/journal.pone.0028712. Epub 2011 Dec 9.
The gene encoding the human formyl peptide receptor 1 (FPR1) is heterogeneous, containing numerous single nucleotide polymorphisms (SNPs). Here, we examine the effect of these SNPs on gene transcription and protein translation. We also identify gene promoter sequences and putative FPR1 transcription factors. To test the effect of codon bias and codon pair bias on FPR1 expression, four FPR1 genetic variants were expressed in human myeloid U937 cells fused to a reporter gene encoding firefly luciferase. No significant differences in luciferase activity were detected, suggesting that the translational regulation and protein stability of FPR1 are modulated by factors other than the SNP codon bias and the variant amino acid properties. Deletion and mutagenesis analysis of the FPR1 promoter showed that a CCAAT box is not required for gene transcription. A -88/41 promoter construct resulted in the strongest transcriptional activity, whereas a -72/41 construct showed large reduction in activity. The region between -88 and -72 contains a consensus binding site for the transcription factor PU.1. Mutagenesis of this site caused significant reduction in reporter gene expression. The PU.1 binding was confirmed in vivo by chromatin immunoprecipitation, and the binding to nucleotides -84 to -76 (TTCCTATTT) was confirmed in vitro by an electrophoretic mobility shift assay. Thus, similar to many other myeloid genes, FPR1 promoter activity requires PU.1. Two single nucleotide polymorphisms at -56 and -54 did not significantly affect FPR1 gene expression, despite differences in binding of transcription factor IRF1 in vitro. Inflammatory mediators such as interferon-γ, tumor necrosis factor-α, and lipopolysaccharide did not increase FPR1 promoter activity in myeloid cells, whereas differentiation induced by DMSO and retinoic acid enhanced the activity. This implies that the expression of FPR1 in myeloid cells is developmentally regulated, and that the differentiated cells are equipped for immediate response to microbial infections.
人类甲酰肽受体 1（FPR1）基因具有异质性，包含许多单核苷酸多态性（SNP）。在这里，我们研究了这些 SNP 对基因转录和蛋白翻译的影响。我们还鉴定了基因启动子序列和潜在的 FPR1 转录因子。为了测试密码子偏好和密码子对偏好对 FPR1 表达的影响，我们将四个 FPR1 遗传变异体表达在融合了萤火虫荧光素酶报告基因的人髓样 U937 细胞中。未检测到荧光素酶活性的显著差异，这表明 FPR1 的翻译调控和蛋白稳定性受到 SNP 密码子偏好和变异氨基酸特性以外的因素调节。FPR1 启动子的缺失和突变分析表明，CCAAT 盒不是基因转录所必需的。-88/41 启动子构建体导致最强的转录活性，而-72/41 构建体的活性大大降低。-88 至-72 之间的区域包含转录因子 PU.1 的一个共有结合位点。该位点的突变导致报告基因表达的显著降低。体内染色质免疫沉淀证实了 PU.1 的结合，体外电泳迁移率变动分析证实了与核苷酸-84 至-76（TTCCTATTT）的结合。因此，与许多其他髓样基因一样，FPR1 启动子活性需要 PU.1。-56 和-54 处的两个单核苷酸多态性尽管在体外转录因子 IRF1 的结合上存在差异，但并未显著影响 FPR1 基因表达。干扰素-γ、肿瘤坏死因子-α和脂多糖等炎症介质不会增加髓样细胞中的 FPR1 启动子活性，而 DMSO 和维甲酸诱导的分化增强了其活性。这意味着 FPR1 在髓样细胞中的表达受到发育调控，分化的细胞能够对微生物感染做出即时反应。
