Two discrete promoters regulate the alternatively spliced human interferon regulatory factor-5 isoforms. Multiple isoforms with distinct cell type-specific expression, localization, regulation, and function.
Interferon regulatory factor-5 (IRF-5) is a mediator of virus-induced immune activation and type I interferon (IFN) gene regulation. In human primary plasmacytoid dendritic cells (PDC), IRF-5 is transcribed into four distinct alternatively spliced isoforms (V1, V2, V3, and V4), whereas in human primary peripheral blood mononuclear cells two additional new isoforms (V5 and V6) were identified. The IRF-5 V1, V2, and V3 transcripts have different noncoding first exons and distinct insertion/deletion patterns in exon 6. Here we showed that V1 and V3 have distinct transcription start sites and are regulated by two discrete promoters. The V1 promoter (P-V1) is constitutively active, contains an IRF-E consensus-binding site, and is further stimulated in virus-infected cells by IRF family members. In contrast, endogenous V3 transcripts were up-regulated by type I IFNs, and the V3 promoter (P-V3) contains an IFN-stimulated responsive element-binding site that confers responsiveness to IFN through binding of the ISGF3 complex. In addition to V5 and V6, we have identified three more alternatively spliced IRF-5 isoforms (V7, V8, and V9); V5 and V6 were expressed in peripheral blood mononuclear cells from healthy donors and in immortalized B and T cell malignancies, whereas expression of V7, V8, and V9 transcripts were detected only in human cancers. The results of this study demonstrated the existence of multiple IRF-5 spliced isoforms with distinct cell type-specific expression, cellular localization, differential regulation, and dissimilar functions in virus-mediated type I IFN gene induction.
Mancl
Margo E
ME
Division of Viral Oncology, The Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
Hu
Guodong
G
Sangster-Guity
Niquiche
N
Olshalsky
Stacey L
SL
Hoops
Katherine
K
Fitzgerald-Bocarsly
Patricia
P
Pitha
Paula M
PM
Pinder
Karen
K
Barnes
Betsy J
BJ
D020121:5' Untranslated Regions; D017398:Alternative Splicing; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D015152:Blotting, Northern; D002460:Cell Line; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics*; D003713:Dendritic Cells / Q000166:cytology; D004285:Dogs; D005091:Exons; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D050835:Interferon Regulatory Factors; D007372:Interferons / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics*; D015533:Transcriptional Activation; D014162:Transfection
D020121:5' Untranslated Regions; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C431713:IRF5 protein, human; D050835:Interferon Regulatory Factors; D009841:Oligonucleotides; D020033:Protein Isoforms; D012333:RNA, Messenger; D014157:Transcription Factors; D007372:Interferons; D008156:Luciferases