Characterization of an alternative exon of the murine T cell receptor beta-chain. Pattern of expression and evolutionary conservation.
In this report, we characterize an alternate gene element of the murine TCR beta-chain. First, we have looked at the expression of the alternate exon, C beta 0, in normal T cell clones, as well as in fetal vs adult whole thymus. The C beta 0 exon is expressed in only 1% or less of TCR-beta messages in four of four mature T cell clones examined. C beta 0 is found at 10-fold higher levels in both fetal and adult thymus mRNA. Thus C beta 0 is developmentally regulated by T cells, although expression of the alternate exon is relatively constant from the fetal thymus to the adult thymus. Second, evolutionary conservation of the C beta 0 gene element was studied in both the rat and the human. The rat beta-locus contains a gene element highly homologous to the mouse C beta 0 gene, but the rat C beta 0 gene contains mutations in both splice sites that probably prevent the gene element from being spliced into mRNA. We have also sequenced the first exon of rat C beta 1, and find that the C beta 0 exon and the intron around C beta 0 are conserved between rat and mouse to the same level as the C beta 1 coding region. The intron around C beta 1, in contrast, shows the decrease in conservation between the two species that is expected for a noncoding region. Analysis of the putative C beta 0-containing region in the human reveals no sequences homologous to the C beta 0 gene element. Because the mouse is the only species that has conserved a functional C beta 0 gene, we conclude that the C beta 0 exon does not play a general role in T cell development.
Dent
A L
AL
Department of Biology, University of California, San Diego, La Jolla 92093.
Fink
P J
PJ
Hedrick
S M
SM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002999:Clone Cells / Q000378:metabolism; D005091:Exons; D005333:Fetus; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics* / Q000302:isolation & purification; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D011919:Rats, Inbred Strains; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000302:isolation & purification; D016693:Receptors, Antigen, T-Cell, alpha-beta; D012689:Sequence Homology, Nucleic Acid; D013601:T-Lymphocytes / Q000378:metabolism; D013950:Thymus Gland / Q000196:embryology / Q000378:metabolism
D007127:Immunoglobulin Constant Regions; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta