Characterization of an Oct1 orthologue in the channel catfish, Ictalurus punctatus: a negative regulator of immunoglobulin gene transcription?

Background: The enhancer (Emu3') of the immunoglobulin heavy chain locus (IGH) of the channel catfish (Ictalurus punctatus) has been well characterized. The functional core region consists of two variant Oct transcription factor binding octamer motifs and one E-protein binding muE5 site. An orthologue to the Oct2 transcription factor has previously been cloned in catfish and is a functionally active transcription factor.

Characterization of two POU transcription factor family members from the urochordate Oikopleura dioica.

Three POU domain containing transcription factors have been cloned from the urochordate Oikopleura dioica. Phylogenetic analysis showed that two of these (OctA1 and OctA2) are closely related members of the class II POU domain family, and one (OctB) is a member of the class III POU domain family. All three transcription factors contained a highly conserved bipartite DNA-binding POU domain with POU specific and POU homeodomains, separated by a linker region.

Regulation of the immunoglobulin heavy chain locus expression at the phylogenetic level of a bony fish: transcription factor interaction with two variant octamer motifs.

Transcriptional control of the IGH locus in teleosts is not fully understood, but evidence from catfish and zebrafish indicates major roles for octamer-binding (Oct) and E-protein transcription factors. A pair of variant octamer motifs in the Emu3' enhancer of the catfish has been shown to be particularly important in driving expression, justifying detailed study of their function. These octamer motifs were examined to determine if they bound Oct2 POU domains in monomeric or dimeric (PORE and MORE) configurations.

Conservation and divergence of the Emicro3' enhancer in the IGH locus of teleosts.

The core region of the Emicro3' transcriptional enhancer that drives the expression of the teleost IGH locus has been characterized functionally in two species, the catfish (Ictalurus punctatus) and the zebrafish (Danio rerio). These studies have suggested important differences: whereas the catfish enhancer acts through an E-box and two octamer motifs, the zebrafish enhancer exerts its major effects through two E-box motifs alone. In this study, the function of the catfish enhancer was reexamined in a broader comparative context within the teleosts.

Oct2 transcription factors in fish--a comparative genomic analysis.

The Oct2 transcription factor is important in driving expression of the IgH locus of the channel catfish, Ictalurus punctatus. Two isoforms, catfish Oct2alpha and Oct2beta, have been characterized at the level of expression and function, but little is known of the structure of the Oct2 gene in catfish. To gain insight into the diversity of Oct2 gene structure and expression in the teleost fish, a comparative genomic analysis of Oct2 was undertaken in the pufferfish (Fugu rubripes) and the zebrafish (Danio rerio).

Evolution of vertebrate E protein transcription factors: comparative analysis of the E protein gene family in Takifugu rubripes and humans.

E proteins are essential for B lymphocyte development and function, including immunoglobulin (Ig) gene rearrangement and expression. Previous studies of B cells in the channel catfish (Ictalurus punctatus) identified E protein homologs that are capable of binding the muE5 motif and driving a strong transcriptional response. There are three E protein genes in mammals, HEB (TCF12), E2A (TCF3), and E2-2 (TCF4).