The early complement components are required for inflammatory responses to tissue injury, microbial infections, and deposited immune complexes. Both the evolution and the resolution of the inflammatory process requires that systemic and local production of the early complement components be tightly controlled to produce a response which contains the pathologic process without damaging healthy tissues. Inappropriate tissue expression might amplify the inflammatory response and damage healthy tissues. The control of expression appears to be regulated at the level of transcription, with both tissue specificity and cytokine responsiveness being tightly controlled. Tissue-specific expression of the early complement components is divergent in all respects except for hepatic and monocytic expression. Our previous work demonstrated that the early complement component promoter regions share four conserved DNA motifs. Electrophoretic mobility shift analyses demonstrated that three of these four motifs bind DNA-binding proteins found in the nuclei of either hepatic or monocytic cells. Recent work demonstrated that the conserved motifs from C1qA, C4A, C2, and C3 are all capable of forming similar DNA- protein complexes on electrophoretic mobility shift analysis consistent with the belief that they interact with the same DNA-binding proteins. The DNA-binding proteins which bind to the first and fourth conserved motifs are zinc dependent, suggesting they may be members of the zinc-finger family of transcription factors. We have cloned a DNA-binding protein which interacts specifically with the third conserved motif and it is a novel gene which thus far has no nucleotide or amino acid sequence homologies with other genes. This suggests that early complement component expression may be regulated by a group of novel transcription factors. We hypothesize that these four con served motifs control early complement component expression in hepatic and monocytic tissues. The goal of this project is to understand the mechanisms governing hepatic and local production of early complement components. These studies will define the role of the four conserved promoter motifs through mutation analyses of the four motifs coupled with cloning of the DNA-binding proteins. We will also study the role of these four motifs in development through the use of a transgenic mouse model. This transgenic mouse contains the LacZ gene under the control of a synthetic promoter consisting of the four conserved motifs and will address the question of whether the four motifs alone are sufficient to direct tissue-specific expression. Developmental utilization of the four motifs will also be addressed using this model. Finally, we will begin to address the question of whether these four motifs were conserved as a unit because the DNA-binding proteins interact with each other to achieve their full effect. Understanding the regulation of early complement component expression will impact not only on the study of complement but is essential to the understanding of inflammation.
| Suriano, April R; Sanford, Amy N; Kim, Nahmah et al. (2005) GCF2/LRRFIP1 represses tumor necrosis factor alpha expression. Mol Cell Biol 25:9073-81 |
