The rat ortholog of the presumptive flounder antifreeze enhancer‐binding protein is a helicase domain‐containing protein

Abstract

The expression of winter flounder liver-type antifreeze protein (wflAFP) genes is tissue-specific and under seasonal and hormonal regulation. The only intron of the major wflAFP gene was demonstrated to be a liverspecific enhancer in both mammalian cell lines and flounder hepatocytes. Element B, the core enhancer sequence, was shown to interact specifically with a liver-enriched transcription factor, CCAAT/enhancer-binding protein a (C/EBPa), as well as a presumptive antifreeze enhancer-binding protein (AEP). In this study, the identity of the rat AEP ortholog was revealed via its DNA±protein interaction with element B. It is a helicasedomain-containing protein, 988 amino acids in length, and is homologous to mouse Smubp-2, hamster Rip-1 and human Smubp-2. The specific binding between element B and AEP was confirmed by South-Western analysis and gel retardation assays. Residues in element B important to this interaction were identified by methylation interference assays. Mutation on one of the residues disrupted the binding between element B and AEP and its enhancer activity was significantly reduced, suggesting that AEP is essential for the transactivation of the wflAFP gene intron. The rat AEP is ubiquitously expressed in various tissues, and the flounder homolog is present as shown by genomic Southern analysis. The potential role of AEP in regulating the flounder AFP gene expression is discussed.

Truncating and Missense Mutations in IGHMBP2 Cause Charcot-Marie Tooth Disease Type 2

“…45 IGHMBP2 contains a DNA-binding domain at position 638À786, including the helicase motifs V and VI 44,46,47 and the nucleic acid-binding R3H motif 48 is involved in immunoglobulin switching, 47 in pre-mRNA processing, 45 and in regulation of transcription by DNA binding. 49 In this respect, IGHMBP2 resembles the SMN protein, which binds directly to DNA and RNA.…”

Characterization of the promoter region of the human IGHMBP2 (Sμbp-2) gene and its response to TPA in HL-60 cells

“…The IGHMBP2 protein has an ATP/GTP-binding motif (Gorbalenya et al, 1988), seven conserved motifs characteristic of DNA helicases or polymerases, and an R3H domain Liepinsh et al, 2003). IGHMBP2 was also reported to bind to the Epstein-Barr virus promoter (Zhang et al, 1999), the rat insulin enhancer (Shieh et al, 1995), anti-freeze enhancer (Miao et al, 2000), and human apoA-I promoter (Mohan et al, 1998), and to regulate DNA replication of the JC virus in glial cells . Moreover, IGHMBP2 was characterized as MAH that is associated with the pre-mRNA splicing complex (Molnar et al, 1997).…”

Tissue specific expression of antifreeze protein and growth hormone transgenes driven by the ocean pout (Macrozoarces americanus) antifreeze protein OP5a gene promoter in Atlantic salmon (Salmo salar)

“…Studies by Miao et al (1998a, b;2000) demonstrated that introns can play an important role in determining the tissue specificity of gene expression. These authors found that the intron in the winter flounder type I AFP genes not only possessed enhancer elements, it also dictated whether expression was relatively ubiquitous, as is the case for the skin type I AFP, or strictly liver specific.…”