Publications

The matrix metalloproteinase gelatinase A plays a central role in several critical physiologic processes, including angiogenesis, tumor invasion/metastasis, and chronic inflammation. We demonstrate that high level gelatinase A expression is mediated by a unique interaction of two developmentally regulated transcription factors, AP2 and YB-1, within a discrete 40-base pair enhancer element (RE-1) located in the 5'-flanking region of the gelatinase A gene. Electrophoretic mobility shift assay studies and immunoprecipitation experiments confirmed a direct interaction of AP2 with this binding sequence in the form of AP2.YB-1 heteromeric complexes. Binding of AP2.YB-1 complexes to the RE-1 sequence results in the formation of extended single-stranded DNA regions and may stabilize DNA conformational changes. Overexpression of YB-1 and AP2 proteins by gelatinase A synthesizing hepatoma HepG2 cells induced a synergistic increase in the RE-1-mediated transcription of nearly 160-fold. Thus, the transcription of gelatinase A is subject to a previously unrecognized interplay of double (AP2) and single-stranded (YB-1) DNA binding transcription factors to yield a highly regulated pattern of gene expression.

Introduction of the MHC class I transgene H-2Dd on C57BL/6 (B6) background conveys NK cell-mediated "missing self" reactivity against transgene-negative cells, and down-regulates expression of the inhibitory receptors Ly49A and Ly49G2 in NK cells. We here present an analysis of transgenic mice expressing chimeric H-2Dd/Ld MHC class I transgenes, and show that the alpha1/alpha2 domains of H-2Dd were necessary and sufficient to induce "missing self" recognition and to down-modulate Ly49A and Ly49G2 receptors. In contrast, transgenes containing the alpha1/alpha2 domains of H-2Ld induced none of these changes, suggesting that not all MHC class I alleles in a host necessarily take part in NK cell education. The lack of effect of the alpha1/alpha2 domains of H-2Ld on NK cell specificity was surprising, considering that both H-2Ld and H-2Dd have been reported to interact with Ly49G2. Therefore, the role of H-2Ld for protection against NK cells expressing Ly49G2 was re-investigated in a transfection system. In contradiction to earlier reports, we show that H-2Dd, but not H-2Ld, abolished killing by sorted Ly49G2+ NK cells, indicating that H-2Ld does not inhibit NK cells via the Ly49G2 receptor.