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Characterisation of RT1-E2, a multigenic family of highly conserved rat non-classical MHC class I molecules initially identified in cells from immunoprivileged sites.

Lau P, Amadou C, Brun H, Rouillon V, McLaren F, Le Rolle AF, Graham M, Butcher GW, Joly E - BMC Immunol. (2003)

Bottom Line: The RT1n MHC haplotype (found in BN rats) carries a single RT1-E2 locus, which lies in the RT1-C/E region of the MHC and displays the typical exon-intron organisation and promoter features seen in other rat MHC class I genes.Compared to other class I molecules, this suggests that RT1-E2 molecules may associate with well defined sets of ligands.Several characteristics point to a certain similarity to the mouse H2-Qa2 and human HLA-G molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFR Claude de Préval, INSERM U563, CHU Purpan, 31300 Toulouse, France. laupoui@pasteur.fr

ABSTRACT

Background: So-called "immunoprivileged sites" are tissues or organs where slow allograft rejection correlates with low levels of expression of MHC class I molecules. Whilst classical class I molecules are recognised by cytotoxic T lymphocytes (CTL), some MHC class I molecules are called "non-classical" because they exhibit low polymorphism and are not widely expressed. These last years, several studies have shown that these can play different, more specialised roles than their classical counterparts. In the course of efforts to characterise MHC class I expression in rat cells obtained from immunoprivileged sites such as the central nervous system or the placenta, a new family of non-classical MHC class I molecules, which we have named RT1-E2, has been uncovered.

Results: Members of the RT1-E2 family are all highly homologous to one another, and the number of RT1-E2 loci varies from one to four per MHC haplotype among the six rat strains studied so far, with some loci predicted to give rise to soluble molecules. The RT1n MHC haplotype (found in BN rats) carries a single RT1-E2 locus, which lies in the RT1-C/E region of the MHC and displays the typical exon-intron organisation and promoter features seen in other rat MHC class I genes. We present evidence that: i) RT1-E2 molecules can be detected at the surface of transfected mouse L cells and simian COS-7 cells, albeit at low levels; ii) their transport to the cell surface is dependent on a functional TAP transporter. In L cells, their transport is also hindered by protease inhibitors, brefeldin A and monensin.

Conclusions: These findings suggest that RT1-E2 molecules probably associate with ligands of peptidic nature. The high homology between the RT1-E2 molecules isolated from divergent rat MHC haplotypes is particularly striking at the level of their extra-cellular portions. Compared to other class I molecules, this suggests that RT1-E2 molecules may associate with well defined sets of ligands. Several characteristics point to a certain similarity to the mouse H2-Qa2 and human HLA-G molecules.

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Alignment of the promoter regions of selected murine class I genes. The promoter sequence for RT1-Al is from AF025309 [40], RT1-Cl: AF025308 [40], H2-Kb: M11847 [39], RT1-E2n: AJ315490, RT1-E2l: AJ537416. The comparison of the various boxed regulatory elements is discussed in the text.
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Figure 5: Alignment of the promoter regions of selected murine class I genes. The promoter sequence for RT1-Al is from AF025309 [40], RT1-Cl: AF025308 [40], H2-Kb: M11847 [39], RT1-E2n: AJ315490, RT1-E2l: AJ537416. The comparison of the various boxed regulatory elements is discussed in the text.

Mentions: RT1-E2 genes appear to follow a somewhat different pattern of expression from those of classical class I molecules. This may be due to divergent sequences in the promoters of these genes determining differential binding of transcription factors. We therefore compared the sequences of the RT1-E2n promoter with those of some other murine class I genes, namely RT1-Al, RT1-Cl and H2-Kb (Fig. 5). We also included in this comparison the sequence of an 840 bp PCR-generated genomic clone of LEW origin, which starts 300 nucleotides upstream of the initiation codon, and finishes in the middle of exon 2. This clone, which was obtained by chance in the course of separate investigations in our laboratory [37], very probably carries the promoter and upstream region of the RT1-E2cl gene since, over the upstream coding sequence where they overlap, it is indistinguishable from the cDNAs from this locus derived from LEW neurospheres and placenta. The RT1-E2n and the RT1-E2cl promoter sequences differ only in one nucleotide just after the TATA box sequence, TGTAAA vs TGTAAG. Because the RT1-E2cl sequence derives from a single clone generated by RT-PCR, we cannot determine whether this difference is genuine or whether it corresponds to a PCR-generated mutation.


Characterisation of RT1-E2, a multigenic family of highly conserved rat non-classical MHC class I molecules initially identified in cells from immunoprivileged sites.

Lau P, Amadou C, Brun H, Rouillon V, McLaren F, Le Rolle AF, Graham M, Butcher GW, Joly E - BMC Immunol. (2003)

Alignment of the promoter regions of selected murine class I genes. The promoter sequence for RT1-Al is from AF025309 [40], RT1-Cl: AF025308 [40], H2-Kb: M11847 [39], RT1-E2n: AJ315490, RT1-E2l: AJ537416. The comparison of the various boxed regulatory elements is discussed in the text.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC183868&req=5

Figure 5: Alignment of the promoter regions of selected murine class I genes. The promoter sequence for RT1-Al is from AF025309 [40], RT1-Cl: AF025308 [40], H2-Kb: M11847 [39], RT1-E2n: AJ315490, RT1-E2l: AJ537416. The comparison of the various boxed regulatory elements is discussed in the text.
Mentions: RT1-E2 genes appear to follow a somewhat different pattern of expression from those of classical class I molecules. This may be due to divergent sequences in the promoters of these genes determining differential binding of transcription factors. We therefore compared the sequences of the RT1-E2n promoter with those of some other murine class I genes, namely RT1-Al, RT1-Cl and H2-Kb (Fig. 5). We also included in this comparison the sequence of an 840 bp PCR-generated genomic clone of LEW origin, which starts 300 nucleotides upstream of the initiation codon, and finishes in the middle of exon 2. This clone, which was obtained by chance in the course of separate investigations in our laboratory [37], very probably carries the promoter and upstream region of the RT1-E2cl gene since, over the upstream coding sequence where they overlap, it is indistinguishable from the cDNAs from this locus derived from LEW neurospheres and placenta. The RT1-E2n and the RT1-E2cl promoter sequences differ only in one nucleotide just after the TATA box sequence, TGTAAA vs TGTAAG. Because the RT1-E2cl sequence derives from a single clone generated by RT-PCR, we cannot determine whether this difference is genuine or whether it corresponds to a PCR-generated mutation.

Bottom Line: The RT1n MHC haplotype (found in BN rats) carries a single RT1-E2 locus, which lies in the RT1-C/E region of the MHC and displays the typical exon-intron organisation and promoter features seen in other rat MHC class I genes.Compared to other class I molecules, this suggests that RT1-E2 molecules may associate with well defined sets of ligands.Several characteristics point to a certain similarity to the mouse H2-Qa2 and human HLA-G molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFR Claude de Préval, INSERM U563, CHU Purpan, 31300 Toulouse, France. laupoui@pasteur.fr

ABSTRACT

Background: So-called "immunoprivileged sites" are tissues or organs where slow allograft rejection correlates with low levels of expression of MHC class I molecules. Whilst classical class I molecules are recognised by cytotoxic T lymphocytes (CTL), some MHC class I molecules are called "non-classical" because they exhibit low polymorphism and are not widely expressed. These last years, several studies have shown that these can play different, more specialised roles than their classical counterparts. In the course of efforts to characterise MHC class I expression in rat cells obtained from immunoprivileged sites such as the central nervous system or the placenta, a new family of non-classical MHC class I molecules, which we have named RT1-E2, has been uncovered.

Results: Members of the RT1-E2 family are all highly homologous to one another, and the number of RT1-E2 loci varies from one to four per MHC haplotype among the six rat strains studied so far, with some loci predicted to give rise to soluble molecules. The RT1n MHC haplotype (found in BN rats) carries a single RT1-E2 locus, which lies in the RT1-C/E region of the MHC and displays the typical exon-intron organisation and promoter features seen in other rat MHC class I genes. We present evidence that: i) RT1-E2 molecules can be detected at the surface of transfected mouse L cells and simian COS-7 cells, albeit at low levels; ii) their transport to the cell surface is dependent on a functional TAP transporter. In L cells, their transport is also hindered by protease inhibitors, brefeldin A and monensin.

Conclusions: These findings suggest that RT1-E2 molecules probably associate with ligands of peptidic nature. The high homology between the RT1-E2 molecules isolated from divergent rat MHC haplotypes is particularly striking at the level of their extra-cellular portions. Compared to other class I molecules, this suggests that RT1-E2 molecules may associate with well defined sets of ligands. Several characteristics point to a certain similarity to the mouse H2-Qa2 and human HLA-G molecules.

Show MeSH