Transcriptional regulation of the porcine miR-17-92 cluster

Alternative Splicing Isoforms of Porcine CREB Are Differentially Involved in Transcriptional Transactivation

The cAMP response element-binding protein (CREB), a basic leucine zipper transcription factor, is involved in the activation of numerous genes in a variety of cell types. The CREB gene is rich in alternative splicing (AS) events. However, studies on the AS of CREB genes in pigs are limited, and few reports have compared the roles of isoforms in activating gene expression. Here, five AS transcripts, V1–5, were characterized by RT-PCR and two, V3 and V5, were new identifications. Both V1 and V2 have all the functional domains of the CREB protein, with similar tissue expression profiles and mRNA stability, suggesting that they have similar roles. The transcriptional transactivation activities of four isoforms encoding complete polypeptides were analyzed on the expression of the B-cell CLL/lymphoma 2-like protein 2 and the poly (A)-binding protein, nuclear 1 genes with a dual-luciferase reporter system, and differential activities were observed. Both V1 and V2 have promoting effects, but their roles are gene-specific. V3 has no effect on the promoter of the two genes, while V4 functions as a repressor. The mechanisms underlying the differential roles of V1 and V2 were analyzed with RNA-seq, and the genes specifically regulated by V1 and V2 were identified. These results will contribute to further revealing the role of CREB and to analyzing the significance of AS in genes.

Speckled 100 kDa gene in pigs: Alternative splicing, subcellular localization, and response to interferon-α stimulation

Speckled 100 kDa (Sp100) plays an important role in the antiviral immune response, however, little is known about porcine Sp100. In this study, porcine Sp100 was cloned and its response to interferon (IFN) α was identified. We obtained the cDNA (V1) of the gene, SP100, and seven alternative splicing variants (V2-8). Isoform V1 encoded a 386 amino acid protein and contained a homogeneously-staining region (HSR) domain. Isoforms V3, 4, 6 and 7 were deletion/insertion variants and contained HSR domain as V1. The splicing of porcine SP100 was very complicated and many transcripts existed as revealed by cloning and minigene analyses. Using GFP-fusion constructs isoforms V1, 3, 4, 6 and 7 were localized to nucleus and the nuclear localization signal was identified as PSNRKRR at positions 331-337 of V1. Porcine SP100 was unevenly distributed in all tissues studied and differentially expressed between pigs with different disease-resistance/susceptibilities. Porcine SP100 was strongly increased by IFNα due to the existence of an IFN-stimulated response element in the promoter. A single nucleotide - 70A > C polymorphism enhanced promoter activity. The results provided the basis for determining the role of Sp100 in antiviral responses and may assist in breeding pigs with high disease-resistance.