Biomedical subjects

J Douhan

Publications and source records attributed to J Douhan.

3 recordsLinked to original sources

PubMed1990

The presence of a DNA binding complex correlates with E beta class II MHC gene expression.

The class II major histocompatibility complex (MHC, Ia) antigens are a family of membrane proteins whose expression is strictly regulated. They have a limited tissue distribution and their expression is regulated both developmentally and in response to external stimuli. Here we report the identification of a DNA binding protein complex (termed complex A) within the murine E beta MHC gene, which is restricted to cells that express Ia antigens. Complex A binding activity is developmentally regulated in cells of the B lineage in accordance with class II expression and is responsive to two different Ia-inducing lymphokines, interferon-gamma in macrophages and interleukin-4 in pre-B cells. The DNA target sequence in complex A includes three previously defined transcriptional motifs W, X and Y, and acts as a cis-acting transcription element. Complex A is present both in cells that are constitutive for class II MHC expression and in cells that have been induced for class II MHC expression. These results suggest that complex A may play a critical role in the regulation of class II MHC gene expression.

Animals↗

PubMed1990

Interferon gamma regulates binding of two nuclear protein complexes in a macrophage cell line.

Interferon gamma (IFN-gamma) is a potent inducer of major histocompatibility complex (MHC) antigens during normal immune responses and in abnormal responses in autoimmune disease. In this report we identify two nuclear factors whose binding to the murine E beta class II MHC beta-chain gene is regulated by this cytokine. IFN-gamma stimulation of murine macrophages results in the appearance of increased binding of one protein complex, complex A, and decreased binding of a second, faster migrating protein complex, complex B. Although the contact residues for both of these proteins lie within the highly conserved Y-box transcriptional element, their binding specificity differs. The protein in complex B is a CCAAT-box-binding protein that may be similar or identical to NF-Y or YB1, previously identified class II Y-box-binding proteins. The DNA sequence requirements for the binding of the slower migrating complex, complex A, are not limited to CCAAT-box sequences but include sequences upstream of the Y box. These upstream sequences are required both for IFN-gamma-induced gene transcription and for IFN-gamma-induced modulation of binding activity. These data suggest a model in which upstream sequences contribute to formation of a lymphokine-regulated complex downstream. The IFN-gamma-induced binding protein described as complex A in this report differs from the IFN-gamma, -alpha, or -beta-induced nuclear factors previously identified.

Animals↗

PubMed1986

How lambda repressor and lambda Cro distinguish between OR1 and OR3.

Although lambda repressor and lambda Cro bind to the same six operators on the phage chromosome, the fine specificities of the two proteins differ: repressor binds more tightly to OR1 than to OR3, and vice versa for Cro. In this paper, we change base pairs in the operators and amino acids in the proteins to analyze the basis for these preferences. We find that these preferences are determined by residues 5 and 6 of the recognition helices of the two proteins and by the amino-terminal arm, in the case of repressor. We also find that the most important base pairs in the operator which enable repressor and Cro to discriminate between OR1 and OR3 are position 3 (for Cro) and positions 5 and 8 (for repressor). These and previous results show how repressor and Cro recognize and distinguish between two related operator sequences.

Amino Acid Sequence↗