The non-histone chromosomal protein HMG-I(Y) contributes to repression of the immunoglobulin heavy chain germ-line epsilon RNA promoter.
The rate of germ-line RNA transcription correlates with the rate of immunoglobulin heavy chain isotype switching. A promoter element for the transcription of RNA from the germ-line mouse immunoglobulin epsilon heavy chain constant region gene is induced by interleukin(IL)-4 and lipopolysaccharide, and is bound at its transcription initiation sites by an IL-4-inducible nuclear protein, NF-BRE. To examine the function of the binding site for this IL-4-inducible complex, substitution mutations were introduced in the promoter. These binding site mutations increased promoter activity and decreased binding of NF-BRE. To investigate the paradox of an IL-4-inducible protein binding to a repressor site in an IL-4-inducible promoter, we determined that the non-histone chromosomal protein HMG-I(Y) binds at the transcription initiation sites of the germ-line epsilon promoter. Assays with antisera against HMG-I(Y) revealed monomeric HMG-I(Y) in nuclear extracts. Cotransfection of an expression construct directing the synthesis of anti-sense HMG-I(Y) RNA also increased promoter activity, consistent with a repressor function of HMG-I(Y). Thus, the data are most consistent with a model in which HMG-I(Y) participates in repression of promoter activity. The effects of IL-4 may include derepression at this site.
Kim
J
J
Department of Cancer Biology, Harvard School of Public Health, Boston.
Reeves
R
R
Rothman
P
P
Boothby
M
M
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000502:physiology*; D007073:Immunoglobulin E / Q000096:biosynthesis / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection / Q000235:genetics
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D007143:Immunoglobulin Heavy Chains; D012333:RNA, Messenger; D011994:Recombinant Proteins; D025741:HMGA1a Protein; D007073:Immunoglobulin E