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An isotype-specific activator of major histocompatibility complex (MHC) class II genes that is independent of class II transactivator.

Douhan J, Lieberson R, Knoll JH, Zhou H, Glimcher LH - J. Exp. Med. (1997)

Bottom Line: We report here that ectopic expression of CIITA cDNAs derived by reverse transcriptase polymerase chain reaction from clone 13 do not restore expression of HLA-DQ in another CIITA-deficient cell line, RJ2.2.5.In addition, no CIITA protein is detectable in clone 13 nuclear extracts.In contrast, somatic cell fusion between clone 13 and RJ2.2.5 restored expression of the HLA-DQ haplotype encoded by the RJ2.2.5 DQB gene.

View Article: PubMed Central - PubMed

Affiliation: Harvard School of Public Health, Department of Cancer Biology, Boston, Massachusetts 02115, USA.

ABSTRACT
Patients with one type of major histocompatibility complex class II combined immunodeficiency have mutations in a gene termed class II transactivator (CIITA), which coordinately controls the transcription of the three major human class II genes, HLA-DR, -DQ, and -DP. However, the experimentally derived B-lymphoblastoid cell line, clone 13, expresses high levels of HLADQ in the absence of HLA-DR and HLA-DP, despite its mapping by complementation analysis to this group. It was possible that one of the clone 13 CIITA alleles bore a mutation that allowed HLA-DQ, but not HLA-DR or -DP transcription. Alternatively, another factor, distinct from CIITA, might control HLA-DQ expression. We report here that ectopic expression of CIITA cDNAs derived by reverse transcriptase polymerase chain reaction from clone 13 do not restore expression of HLA-DQ in another CIITA-deficient cell line, RJ2.2.5. In addition, no CIITA protein is detectable in clone 13 nuclear extracts. In contrast, somatic cell fusion between clone 13 and RJ2.2.5 restored expression of the HLA-DQ haplotype encoded by the RJ2.2.5 DQB gene. Taken together, these data demonstrate the existence of an HLA-DQ isotype-specific trans-acting factor, which functions independently of CIITA.

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MHC class II expression directed by chimeric CIITA cDNAs  tranfected into RJ 2.2.5 cells. Expression plasmids bearing chimeric CIITA  cDNA derived from the indicated sources were stably transfected into  RJ2.2.5 cells and analyzed for the expression of HLA-DR, -DP, and -DQ  after selection in hygromycin. Surface expression of HLA antigens was  detected by flow cytometry.
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Figure 4: MHC class II expression directed by chimeric CIITA cDNAs tranfected into RJ 2.2.5 cells. Expression plasmids bearing chimeric CIITA cDNA derived from the indicated sources were stably transfected into RJ2.2.5 cells and analyzed for the expression of HLA-DR, -DP, and -DQ after selection in hygromycin. Surface expression of HLA antigens was detected by flow cytometry.

Mentions: The various chimeric CIITA cDNAs used for these transfection studies and the results of flow cytometric analysis of RJ2.2.5 cells transfected with either pCMV.CIITA, or with the chimeric constructs are shown in Fig. 4. As shown previously, transfection of wild-type CIITA into RJ2.2.5 caused reexpression of HLA-DR, -DQ, and -DP. Notably, chimeric CIITA cDNAs bearing either the 4-bp or the 93-bp deletion were unable to recapitulate the pattern of HLA-D antigen expression seen in clone 13. Interestingly, a CIITA cDNA bearing the 147-bp deletion previously identified as a splice variant was fully active, despite the fact that the deletion region maps to a portion of the proline–serine–threonine (PST)–rich domain that has been shown to be necessary for optimal transactivaton by CIITA (16). Thus, the mutations in CIITA in the clone 13 alleles rendered them completely unable to transactivate all three HLA-D genes. These data suggested that the expression of HLA-DQ in clone 13 may be regulated by a novel transacting factor different from and independent of CIITA.


An isotype-specific activator of major histocompatibility complex (MHC) class II genes that is independent of class II transactivator.

Douhan J, Lieberson R, Knoll JH, Zhou H, Glimcher LH - J. Exp. Med. (1997)

MHC class II expression directed by chimeric CIITA cDNAs  tranfected into RJ 2.2.5 cells. Expression plasmids bearing chimeric CIITA  cDNA derived from the indicated sources were stably transfected into  RJ2.2.5 cells and analyzed for the expression of HLA-DR, -DP, and -DQ  after selection in hygromycin. Surface expression of HLA antigens was  detected by flow cytometry.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196342&req=5

Figure 4: MHC class II expression directed by chimeric CIITA cDNAs tranfected into RJ 2.2.5 cells. Expression plasmids bearing chimeric CIITA cDNA derived from the indicated sources were stably transfected into RJ2.2.5 cells and analyzed for the expression of HLA-DR, -DP, and -DQ after selection in hygromycin. Surface expression of HLA antigens was detected by flow cytometry.
Mentions: The various chimeric CIITA cDNAs used for these transfection studies and the results of flow cytometric analysis of RJ2.2.5 cells transfected with either pCMV.CIITA, or with the chimeric constructs are shown in Fig. 4. As shown previously, transfection of wild-type CIITA into RJ2.2.5 caused reexpression of HLA-DR, -DQ, and -DP. Notably, chimeric CIITA cDNAs bearing either the 4-bp or the 93-bp deletion were unable to recapitulate the pattern of HLA-D antigen expression seen in clone 13. Interestingly, a CIITA cDNA bearing the 147-bp deletion previously identified as a splice variant was fully active, despite the fact that the deletion region maps to a portion of the proline–serine–threonine (PST)–rich domain that has been shown to be necessary for optimal transactivaton by CIITA (16). Thus, the mutations in CIITA in the clone 13 alleles rendered them completely unable to transactivate all three HLA-D genes. These data suggested that the expression of HLA-DQ in clone 13 may be regulated by a novel transacting factor different from and independent of CIITA.

Bottom Line: We report here that ectopic expression of CIITA cDNAs derived by reverse transcriptase polymerase chain reaction from clone 13 do not restore expression of HLA-DQ in another CIITA-deficient cell line, RJ2.2.5.In addition, no CIITA protein is detectable in clone 13 nuclear extracts.In contrast, somatic cell fusion between clone 13 and RJ2.2.5 restored expression of the HLA-DQ haplotype encoded by the RJ2.2.5 DQB gene.

View Article: PubMed Central - PubMed

Affiliation: Harvard School of Public Health, Department of Cancer Biology, Boston, Massachusetts 02115, USA.

ABSTRACT
Patients with one type of major histocompatibility complex class II combined immunodeficiency have mutations in a gene termed class II transactivator (CIITA), which coordinately controls the transcription of the three major human class II genes, HLA-DR, -DQ, and -DP. However, the experimentally derived B-lymphoblastoid cell line, clone 13, expresses high levels of HLADQ in the absence of HLA-DR and HLA-DP, despite its mapping by complementation analysis to this group. It was possible that one of the clone 13 CIITA alleles bore a mutation that allowed HLA-DQ, but not HLA-DR or -DP transcription. Alternatively, another factor, distinct from CIITA, might control HLA-DQ expression. We report here that ectopic expression of CIITA cDNAs derived by reverse transcriptase polymerase chain reaction from clone 13 do not restore expression of HLA-DQ in another CIITA-deficient cell line, RJ2.2.5. In addition, no CIITA protein is detectable in clone 13 nuclear extracts. In contrast, somatic cell fusion between clone 13 and RJ2.2.5 restored expression of the HLA-DQ haplotype encoded by the RJ2.2.5 DQB gene. Taken together, these data demonstrate the existence of an HLA-DQ isotype-specific trans-acting factor, which functions independently of CIITA.

Show MeSH
Related in: MedlinePlus