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S Roys

Publications and source records attributed to S Roys.

5 recordsLinked to original sources
PubMed2001

Self-association of CIITA and its transactivation potential.

The major histocompatibility complex (MHC) class II transactivator (CIITA) regulates the expression of genes involved in the immune response, including MHC class II genes and the interleukin-4 gene. Interactions between CIITA and sequence-specific, DNA-binding proteins are required for CIITA to function as an activator of MHC class II genes. CIITA also interacts with the coactivators CBP (also called p300), and this interaction leads to synergistic activation of MHC class II promoters. Here, we report that CIITA forms complexes with itself and that a central region, including the GTP-binding domain is sufficient for self-association. Additionally, this central region interacts with the C-terminal leucine-rich repeat as well as the N-terminal acidic domain. LXXLL motifs residing in the GTP-binding domain are essential for self-association. Finally, distinct differences exist among various CIITA mutant proteins with regard to activation function, subcellular localization, and association with wild-type protein and dominant-negative potential.

Amino Acid Motifs↗
PubMed2000

MHC class II transactivator inhibits IL-4 gene transcription by competing with NF-AT to bind the coactivator CREB binding protein (CBP)/p300.

The MHC class II transactivator (CIITA) activates the expression of multiple genes involved in Ag presentation, but inhibits Th2-type cytokine production, including IL-4, during Th1 cell differentiation. Th1 cells derived from CIITA-deficient mice produce both Th1- and Th2-type cytokines, and the introduction of CIITA to Th2 cells down-regulates Th2-type cytokine gene transcription. Here we show that the IL-4 promoter is regulated by multiple protein-protein interactions among CIITA, NF-AT, and coactivator CBP/p300. The introduction of CBP/p300 and NF-AT enhances the IL-4 promoter activity, and this activation was repressed by CIITA. Furthermore, our data show that CIITA competes with NF-AT to bind CBP/p300 and that this competition dramatically influences transcriptional activation of the IL-4 promoter. We identified two domains of CIITA that interact with two distinct domains of CBP/p300 that are also recognized by NF-AT. CIITA mutants that retain the ability to interact with CBP/p300 are sufficient to inhibit NF-AT-mediated IL-4 gene expression.

Binding, Competitive↗
PubMed1999

A novel role for the major histocompatibility complex class II transactivator CIITA in the repression of IL-4 production.

Class II transactivator (CIITA) is known as a coactivator for MHC class II gene expression in antigen-presenting cells. Surprisingly, when CIITA-/- CD4 T cells were stimulated in the presence of IL-12, they produced not only IFNgamma but also high levels of IL-4. The IL-4 production is due to the accumulation of IL-4 gene transcripts in Th1 cells. This transcriptional control is observed in T cells differentiating to the Th1 but not Th2 lineage, consistent with induction of expression of the CIITA gene in T cells by IFNgamma. Thus, in addition to its role in transactivation of genes involved in antigen presentation, CIITA plays a critical role during the T cell differentiation by negatively regulating the IL-4 gene transcription.

Animals↗
PubMedDate not supplied

Phantom evaluation of angiographer performance using low frame rate acquisition fluoroscopy.

The authors have investigated the effect of 5 frames/s television fluoroscopy on the time required to selectively catheterize five test arteries in an angiographic phantom. Here, 5 frames/s acquisition was accomplished by sampling frames from a 30 frames/s video signal. Sampled frames were stored in a video memory which provided continuous display to the fluoroscopist between samples. The test phantom was a plastic model of an aorta with branching vessels immersed in an isodense suspension of barium in water. For four of the five vessels there was no significant difference in time required for catheter placement between 30 frames/s and 5 frames/s.

Catheterization↗