IRF2BP2 3'UTR Polymorphism Increases Coronary Artery Calcification in Men

Functional characterization of the disease-associated CCL2 rs1024611G-rs13900T haplotype: The role of the RNA-binding protein HuR

CC-chemokine ligand 2 (CCL2) is involved in the pathogenesis of several diseases associated with monocyte/macrophage recruitment, such as HIV-associated neurocognitive disorder (HAND), tuberculosis, and atherosclerosis. The rs1024611 (alleles:A>G; G is the risk allele) polymorphism in the CCL2 cis-regulatory region is associated with increased CCL2 expression in vitro and ex vivo, leukocyte mobilization in vivo, and deleterious disease outcomes. However, the molecular basis for the rs1024611-associated differential CCL2 expression remains poorly characterized. It is conceivable that genetic variant(s) in linkage disequilibrium (LD) with rs1024611 could mediate such effects. Previously, we used rs13900 (alleles:_C>T) in the CCL2 3' untranslated region (3' UTR) that is in perfect LD with rs1024611 to demonstrate allelic expression imbalance (AEI) of CCL2 in heterozygous individuals. Here we tested the hypothesis that the rs13900 could modulate CCL2 expression by altering mRNA turnover and/or translatability. The rs13900 T allele conferred greater stability to the CCL2 transcript when compared to the rs13900 C allele. The rs13900 T allele also had increased binding to Human Antigen R (HuR), an RNA-binding protein, in vitro and ex vivo. The rs13900 alleles imparted differential activity to reporter vectors and influenced the translatability of the reporter transcript. We further demonstrated a role for HuR in mediating allele-specific effects on CCL2 expression in overexpression and silencing studies. The presence of the rs1024611G-rs13900T conferred a distinct transcriptomic signature related to inflammation and immunity. Our studies suggest that the differential interactions of HuR with rs13900 could modulate CCL2 expression and explain the interindividual differences in CCL2-mediated disease susceptibility.

An IRF2BP member (CgIRF2BP) involved in negative regulation of CgIFNLP expression in oyster Crassostrea gigas

The IRF2BP family of transcription regulators act as corepressor molecules by inhibiting both enhancer-activated and basal transcription involving in many biological contexts. In the present study, an IRF2BP homologue (CgIRF2BP) was identified from oyster C. gigas. Its open reading frame is of 1809 bp encoding a polypeptide of 602 amino acids, which contains an IRF-2BP1_2 domain and a RING domain. The mRNA transcripts of CgIRF2BP were detected in all tested tissues with highest level in haemocytes (28.99-fold of that in mantle, p < 0.05). After poly (I:C) stimulation, the expression level of CgIRF2BP was significantly down-regulated at 3 h (0.50-fold of that in control group, p < 0.001) and gradually increased from 6 h to 48 h (2.69-fold of that in control group, p < 0.01). The recombinant protein of CgIRF2BP (rCgIRF2BP) showed high affinity to both rCgIRF1 and rCgIRF8 with Kd value of 1.02 × 10^-7 and 2.09 × 10^-7, respectively. In CgIRF2BP-RNAi oysters, the mRNA expression of CgIFNLP, CgMx1, CgViperin and CgIFI44L were significantly increased after poly (I:C) stimulation, which were 2.88 (p < 0.01), 1.83 (p < 0.05), 2.47 (p < 0.05), and 1.99-fold (p < 0.01) of that in EGFP group, respectively. These findings suggested that CgIRF2BP negatively regulated CgIFNLP expression by binding with CgIRF1 and CgIRF8.

Savior Siblings Might Rescue Fetal Lethality But Not Adult Lymphoma in Irf2bp2-Null Mice

Interferon regulatory factor 2 binding protein 2 (Irf2bp2), a co-repressor of Irf2, is required for fetal hepatic erythropoiesis through the expansion of erythromyeloid progenitors. Mice with germline ablation of the entire Irf2bp2 transcript produced no viable Irf2bp2-null pups in first litters. In subsequent litters, fewer than 1/3 of the expected Irf2bp2-null pups were born and half survived to adulthood. As in humans with somatic mutations in IRF2BP2, adult Irf2bp2-null mice developed lymphoma. Transcriptome profiling of liver, heart, and skeletal muscle from Irf2bp2-null adult mice revealed a predominant upregulation of interferon-responsive genes. Of interest, hematopoietic stem cell-enriched transcription factors (Etv6, Fli1, Ikzf1, and Runx1) were also elevated in Irf2bp2-null livers. Intriguingly, Irf2bp2-positive mwfi 2yeloid (but not lymphoid) cells were detected in the livers of adult Irf2bp2-null mice. In female Irf2bp2-null mice, these cells carried a Y chromosome while in male Irf2bp2-null livers, no cells with Barr bodies (inactivated X chromosomes) were detected, indicating that Irf2bp2-positive erythromyeloid cells might be acquired only from male siblings of prior litters by transmaternal microchimerism. These cells likely rescue the deficit in fetal erythropoiesis, but not adult-onset lymphomagenesis, caused by Irfb2p2 ablation.