Major histocompatibility complex class I genes in murine fibrosarcoma IC9 are down regulated at the level of the chromatin structure.
AUTOR(ES)
Maschek, U
RESUMO
The fibrosarcoma IC9 is deficient in the expression of the major histocompatibility complex class I genes Kb, Kk, and Dk and expresses only the Db molecule. Because class I deficiency may enable tumor cells to escape the immune response by cytotoxic T lymphocytes, we investigated why the class I genes are not expressed. Expression of the silent class I genes could not be induced, but all known DNA-binding factors specific for class I genes could be detected in nuclear extracts of IC9 cells. After cloning of the silent Kb gene from the IC9 cells and subsequent transfection of this cloned Kb gene into LTK- and IC9 cells, normal Kb antigens were expressed on the cell surface of both cell lines. Digestion of the chromatin of IC9 cells with micrococcal nuclease and DNase I showed a decreased nuclease sensitivity of the silent class I genes in comparison with active genes and the absence of DNase I hypersensitive sites in the promoter region of the silent Dk gene. These findings demonstrate that class I expression is turned off by a cis-acting regulatory mechanism at the level of the chromatin structure.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=362789Documentos Relacionados
- Concerted evolution of class I genes in the major histocompatibility complex of murine rodents.
- Down-regulation of major histocompatibility complex class I synthesis by murine cytomegalovirus early gene expression.
- Ia+ murine epidermal Langerhans cells are deficient in surface expression of the class I major histocompatibility complex.
- Structure, function, and evolution of mouse TL genes, nonclassical class I genes of the major histocompatibility complex.
- Major histocompatibility complex class I genes of the coelacanth Latimeria chalumnae.