Journal
HUMAN IMMUNOLOGY
Volume 63, Issue 7, Pages 588-601Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/S0198-8859(02)00400-7
Keywords
CIITA; class II MHC; leucine-rich repeats; transcription
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Funding
- NIAID NIH HHS [AI41751, AI45580, AI29564] Funding Source: Medline
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Activation of class II major histocompatibility complex (MHC) gene expression is regulated by a master regulator, class II transcriptional activator (CIITA). Transactivation by CIITA requires its nuclear import. This Study will address a mechanistic role for the leucine-rich repeats (LRR) of CIII-A in regulating nuclear translocation by Mutating 12 individual consensus-motif leucine residues in both its alpha-motifs and beta-motifs. While some leucine mutations in the LRR motif of CIITA cause congruent loss of transactivation function and nuclear import, other alanine substitutions in both the a-helices and the beta-sheets have normal transactivation function but a loss of nuclear accumulation (i.e., functional mutants). This seeming paradox is resolved by the observations that nuclear accumulation of these functional mutants does Occur but is significantly less than wild-type. This difference is revealed only in the presence of leptomycin B and actinomycin D, which permit examination of nuclear accumulation unencumbered by nuclear export and new CIITA synthesis. Further analysis of these mutants reveals that at limiting concentrations of CIITA, a dramatic difference in transactivation function between Mutants and wild-type CIITA is easily detected, in agreement with their lowered nuclear accumulation. These experiments reveal an interesting aspect of LRR in controlling the amount of nuclear accumulation. (C) American Society for Histocompatibility and Immunogenetics, 2002. Published by Elsevier Science Inc.
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