ИСТИНА

Introduction: SLAMF1 (CD150) is a member of a family of costimulatory receptors expressed on a variety of hematopoietic cells. SLAMF1 is highly expressed on mature activated lymphocytes and is involved in germinal centre formation together with other costimulatory molecules and characteristic TFH cytokines such as IL-6, IL-21 and IL-23. Materials and methods: We used 5'-RACE, qRT-PCR and data mining to estimate relative abundance of SLAMF1 mRNA isoforms in human B-cell lines; luciferase reporter assays to measure activity of promoter and enhancer regions , as well as translation activity of the isoform mRNAs; bioinformatics, ChIP and pull-down assays to assess binding of transcription factors to DNA. Results: Human SLAMF1 gene contains a number of binding sites for relevant transcription factors in the functionally important promoter region driving expression of functionally significant (translationaly active) short mRNA isoforms, and at least two potent transcriptional enhancers. Mutations of either Sp1, Stat6, IRF4, NFkB or PU.1 predicted sites resulted in a statistically significant but modest decrease in the promoter activity; in contrast, EBF1 promoter mutant lost almost 90% of the activity. In addition, each of the two enhancers also contained strong EBF1 binding sites. Conclusions: EBF1 is crucial for SLAMF1 gene expression in human B cells. Interestingly, mouse SLAMF1 gene critically depends on EBF1 as well, however there is no EBF1 site in the promoter, and introduction of human EBF1 binding sequence into the homologous position further increases the activity of mouse SLAMF1 promoter. The study is supported by grant 14-25-00160 from Russian Science Foundation.