EXPRESSION OF THE HUMAN GENE CODING FOR THE ALPHA-CHAIN OF C4B-BINDING PROTEIN, C4BPA, IS CONTROLLED BY AN HNF1-DEPENDENT HEPATIC-SPECIFIC PROMOTER
Authors: ARENZANA, N; DECORDOBA, SR; REYCAMPOS, J
C4b-binding protein (C4BP) is an abundant oligomeric plasma glycoprotein which controls the activation of the complement cascade through the classical pathway. In humans, the majority form of C4BP is composed of seven alpha-chains and one beta-chain, covalently linked by their C-termini. C4BP is mainly expressed in the liver. We have previously cloned and characterized the structure of the genes encoding the alpha and beta chains, C4BPA and C4BPB, respectively. Here we addressed the characterization of the mechanisms controlling the hepatic restricted expression of the C4BPA gene. We found that the C4BPA promoter is contained within the first 369 bp upstream of the transcription start site. The activity of this promoter is restricted to hepatic cells in transfection experiments. The hepatic transcription factor HNF1 interacts with a region of this promoter at -38 bp. This region is absolutely required for the activity of this promoter, suggesting that HNF1 is essential for the hepatic activity of the C4BPA promoter. We speculate that this extreme requirement of HNF1 for the activity of the human C4BPA promoter is related to the fact that this promoter lacks a TATA box.
CHROMOSOME ASSIGNMENTS OF THE GENES FOR GLUCOCORTICOID RECEPTOR, MYELIN BASIC-PROTEIN, LEUKOCYTE COMMON ANTIGEN, AND TRPM2 IN THE RAT
Authors: GOLDNERSAUVE, A; SZPIRER, C; SZPIRER, J; LEVAN, G; GASSER, DL
We have utilized rat-mouse somatic cell hybrids to make chromosomal assignments for the glucocorticoid receptor (GR), myelin basic protein (MBP), leukocyte common antigen (LCA), and testosterone-repressed prostate message-2 (TRPM2) genes in the rat. The genes for GR and MBP both map on chromosome 18 of the rat, which corresponds to the mapping of both genes on chromosome 18 of the mouse. The gene for LCA maps on chromosome 13, which is where C4b-binding protein beta-chain (C4BPB), coagulation factor V (F5), and renin have previously been assigned. This linkage group appears to be homologous to a substantial portion of mouse chromosome 1 and human chromosome 1q. Finally, the TRPM2 gene has been assigned to rat chromosome 15.