The Gene of Chicken Axonin-1. Complete Structure and Analysis of the Promoter

Abstract

We have isolated and characterised the gene encoding the chicken axonal cell adhesion molecule axonin-1. This gene comprises 23 exons distributed over approximately 40 kb. Each of the six immunoglobulin-like domains and the four fibronectin-type-III-like domains of axonin-1 is encoded by two exons. The introns between two domains are exclusively phase I. Their exon/intron borders correspond to the domain borders of the protein, suggesting that the gene of axonin-1 had been generated by exon shuffling. Three transcripts with a length of 4.3 kb, 5 kb, and 8 kb are found, and we provide evidence that they result from alternative use of polyadenylation signals. In situ hybridization revealed co-localisation of these transcripts in time and space in the developing chicken retina. Several identical transcription initiation sites were found in retina, brain, and cerebellum by RNase protection assay and anchored polymerase chain reaction. By transfection of HeLa cells, rat PC-12 phaeochromocytoma cells, and chicken embryonic fibroblasts with serially truncated segments of the 5'-flanking region linked to a luciferase reporter gene, we have found that the sequence from -91 to +56 relative to the transcription initiation site is sufficient to promote efficient gene expression. Tissue-specific expression of the axonin-1 gene seems to be regulated in part by sequences more than 1 kb upstream of the transcription initiation site. As revealed by computer analysis, the sequence immediately upstream of exon 1 contains an AP-2 binding site, a tumor phorbol-ester-responsive element, and a homeodomain protein binding site, but no canonical TATA box. A second AP-2 binding site and a homeodomain protein binding site are located within exon 1.

Cloning and Functional Characterization of DSCAML1, a Novel DSCAM-like Cell Adhesion Molecule That Mediates Homophilic Intercellular Adhesion

“…The human DSCAML1 gene contains 32 exons. In Ig superfamily members such as NCAM, axonin-1, and F11, FNIII-like domains are encoded by two exons (37)(38)(39). In contrast, the number of exons coding for one FNIII-like domain in DSCAML1 appears to be variable, as was previously observed for DSCAM (26).…”

Organization of the Neurofascin Gene and Analysis of Developmentally Regulated Alternative Splicing

“…Exons 1 and 2 are separated by an unusually long intron of 29 kb in length. A large first intron is a feature that is also found within the related chick NCAM (38 kb within a gene of 85 kb in length), chick axonin-1 (Ϸ15/40 kb) and chick F11 (more than 10/100 kb) (22,27,28). The transmembrane domain resides on exon 30, and the cytoplasmic domain is located on three exons 31 to 33.…”

“…Sequencing of exons and the respective splice sites indicate that each of the neurofascin extracellular domains is encoded by two exons. Single Ig-like domains can be encoded either by one exon as exemplified for the Ig-like domains of carcinoembryonic antigen CEA, (40), MAG (41), Thy-1, the Fc receptors, CD28, CTLA4, B7-1, the immunoglobulins themselves or CD8 (42,43), or by two exons as described for NCAM, axonin-1, F11, or P o (19,20,22,23,(27)(28)(29). Characteristics for both groups have been found for DCC (44), the leukocyte-common antigen-related molecule (LAR) (45), perlecan (46), and the fibroblast growth factor receptor 1, where within the same polypeptide a single Ig-like domain is encoded either by one or by two exons (45,47).…”

“…32 neurofascin nearly full-length open reading frames obtained from the brain of E6 chick embryos and 106 cDNA clones from E16 chick embryos were analyzed with respect to the expression of the alternatively spliced exons 3,8,17,22,23,26,27,28,29, and 32 ( Fig. 5; results for the exon 22 encoding the NH 2 -terminal half of the third FNIII-like repeat are not included as it behaved identical to exon 23 which encodes the COOH-terminal half of this FNIII-like domain).…”

Thyroid hormone regulates TAG‐1 expression in the developing rat brain

“…Very little is known about how the expression of TAG‐1 is controlled, although in vitro promoter analysis studies have identified regions upstream of the first exon that will direct expression in transfected cultured lines (Giger et al ., 1995; Kozlov et al ., 1995).…”