Transcriptional activation of the human cytotoxic serine protease gene CSP-B in T lymphocytes

Type 1 Interferons Potentiate Human CD8+ T-Cell Cytotoxicity Through a STAT4- and Granzyme B-Dependent Pathway

Events defining the progression to human type 1 diabetes (T1D) have remained elusive owing to the complex interaction between genetics, the immune system, and the environment. Type 1 interferons (T1-IFN) are known to be a constituent of the autoinflammatory milieu within the pancreas of patients with T1D. However, the capacity of IFNα/β to modulate human activated autoreactive CD8⁺ T-cell (cytotoxic T lymphocyte) responses within the islets of patients with T1D has not been investigated. Here, we engineer human β-cell-specific cytotoxic T lymphocytes and demonstrate that T1-IFN augments cytotoxicity by inducing rapid phosphorylation of STAT4, resulting in direct binding at the granzyme B promoter within 2 h of exposure. The current findings provide novel insights concerning the regulation of effector function by T1-IFN in human antigen-experienced CD8⁺ T cells and provide a mechanism by which the presence of T1-IFN potentiates diabetogenicity within the autoimmune islet.

Perforin/granzyme-dependent and independent mechanisms are both important for the development of graft-versus-host disease after murine bone marrow transplantation

Graft-versus-host disease (GvHD) is the major limiting toxicity of allogeneic bone marrow transplantation. T cells are important mediators of GvHD, but the molecular mechanisms that they use to induce GvHD are controversial. Three effector pathways have been described for cytotoxic T lymphocytes: one requires perforin and granzymes, the second Fas (APO-1; CD95) and its ligand. Thirdly, secreted molecules (e.g., TNF-alpha, gamma-IFN) can also mediate cytotoxicity. Together, these mechanisms appear to account for virtually all cytotoxicity induced by activated CTL in standard in vitro lytic assays. Using transplants across histocompatibility barriers, we were able to analyze the contributions of these effector molecules to cell-mediated cytotoxicity in vivo in a GvHD model. We found that Fas ligand is an important independent mediator of class II-restricted acute murine GvHD, while perforin/granzyme-dependent mechanisms have only a minor role in that compartment. In contrast, perforin/ granzyme-dependent mechanisms are required for class I-restricted acute murine GvHD, while Fas ligand is not. The perforin/granzyme pathway may therefore represent a novel target for anti-GvHD drug design. In support of this approach, we provide additional data suggesting that specific perforin/granzyme inhibitors should not adversely affect hematopoietic recovery after transplantation.

Identification of human granzyme B promoter regulatory elements interacting with activated T-cell-specific proteins: implication of Ikaros and CBF binding sites in promoter activation

Granzyme B serine protease is found in the granules of activated cytotoxic T cells and in natural and lymphokine-activated killer cells. This protease plays a critical role in the rapid induction of target cell DNA fragmentation. The DNA regulatory elements that are responsible for the specificity of granzyme B gene transcription in activated T-cells reside between nt -148 and +60 (relative to the transcription start point at +1) of the human granzyme B gene promoter. This region contains binding sites for the transcription factors Ikaros, CBF, Ets, and AP-1. Mutational analysis of the human granzyme B promoter reveals that the Ikaros binding site (-143 to -114) and the AP-1/CBF binding site (-103 to -77) are essential for the activation of transcription in phytohemagglutinin-activated peripheral blood lymphocytes, whereas mutation of the Ets binding site does not affect promoter activity in these cells.

Cloning and characterization of a novel NK cell-specific serine protease gene and its functional 5'-flanking sequences

Rat natural killer cell Met-ase-1 (RNK-Met-1) is a 30,000 M(r) serine protease (granzyme) found in the cytolytic granules of CD3- large granular lymphocytes (LGL) with natural killer (NK) activity. To characterize the genomic sequences responsible for the CD3- LGL-restricted expression of this gene, we screened a rat genomic library with RNK-Met-1 cDNA, and obtained bacteriophage clones that contained the RNK-Met-1 gene. The RNK-Met-1 gene comprises 5 exons and spans approximately 5.2 kilobases (kb), exhibiting a similar structural organization to a class of CTL-serine proteases with protease catalytic residues encoded near the borders of exons 2, 3, and 5. The 5'-flanking region of the RNK-Met-1 gene contains a number of putative promoter and enhancer regulatory elements and shares several regions of homology with the 5'-flanking region of the mouse perforin gene. We have prepared nested deletions from approximately 3.3 kb of the 5'-flanking region of the RNK-Met-1 gene, and inserted these upstream of the chloramphenicol acetyltransferase (CAT) reporter gene. These 5'-flanking RNK-Met-1-CAT constructs were transiently transfected into rat LGL leukemia, T-lymphoma, and basophilic leukemia cell lines. The transcriptional activity of the RNK-Met-1 5'-flanking region was strong, restricted to the RNK-16 LGL leukemia and controlled by several positive cis-acting regions spread over at least 3.3 kb. The longest and most active 5'-flanking region (-3341 to -33) was also used to drive specific expression of beta-galactosidase in RNK-16. These data are consistent with the NK cell-specific expression of RNK-Met-1 and suggest the potential utility of this gene promoter in the development of transgene models of NK cell biology in vivo.

Specific inhibition of granzyme B by parainfluenza virus type 3

T-cell-mediated cytotoxicity is an important means of defense against viral pathogens; however, several viruses possess mechanisms to disrupt cytotoxicity, thereby allowing them to avoid immune clearance. These viruses have been shown to inhibit cytotoxicity by interfering with the capacity of T lymphocytes to specifically recognize infected cells. An alternative mechanism for virally induced cytotoxic dysfunction is identified in this report. We show that parainfluenza virus type 3, a negative-stranded RNA virus, can inhibit cytotoxicity by causing a defect in the cytotoxic effector apparatus. This defect is identified as a selective inhibition of granzyme B mRNA.

Structure and function of the murine beta-globin locus control region 5' HS-3

We previously identified the murine homologue of the human beta-globin Locus Control Region (LCR) 5' HS-2. The lambda clone containing murine 5' HS-2 extends approximately 12 kb upstream from this site; here, we report the sequence of this entire upstream region. The murine homologue of 5' HS-3 is located approximately 16.0 kb upstream from the mouse epsilon y-globin gene, but no region homologous to human 5' HS-4 was present in our clone. Using a reporter system consisting of a human gamma-globin promoter driving the neomycin phosphotransferase gene (gamma-neo), we tested murine LCR fragments extending from -21 to -9 kb (with respect to the epsilon y-globin gene cap site) for activity in classical enhancer and integration site assays in K562 and MEL cells. 5' HS-2 behaved as a powerful enhancer and increased the number of productive integration events (as measured by a colony assay) in both K562 and MEL cells. 5' HS-3 had no activity in K562 cells or in transiently transfected MEL cells, but was nearly as active as 5' HS-2 in the MEL cell colony assay. Two additional tests confirmed the identification of murine 5' HS-3: first, a DNA fragment containing 5' HS-3 confers copy number-dependent, integration-site independent inducibility on a linked beta-globin gene in the MEL cell environment. Secondly, a strong DNAseI hypersensitive site maps to the location of the 5' HS-3 functional core in chromatin derived from MEL cells. Collectively, these data suggest that we have identified the murine homologue of human 5' HS-3, and that this site is functional when integrated into the chromatin of MEL cells but not K562 cells. 5' HS-3 may therefore contain information that contributes to the development-specific expression of the beta-like globin genes.

Transcription of two cytotoxic cell protease genes is under the control of different regulatory elements

Precursor cytotoxic T lymphocytes are activated upon interaction with antigen and interleukin 2. The development of the mature killer cell phenotype is achieved by the transcription of a number of function related genes including those encoding a family of cytotoxic cell proteases (CCP). Two of these proteases, CCP1 and CCP2 encoded by C11 and B10, are shown in this report to contain cell-specific transcriptional regulatory elements within their 5'-flanking regions. Two positive regulatory sequences were mapped for C11 (-682 to -427 and -243 to -112) and one for B10 (-279 to -189). In addition each flanking region contains a region of DNA (B10 -1617 to -1049 and C11 -427 to -243) that has a negative influence on transcription. The positive regions do not appear to correspond to any previously characterized regulatory elements but do map to the same region as DNase I hypersensitive sites. When ligated to heterologous promoters these elements can still stimulate transcription but cell-specificity of expression is lost. In addition the conbination of positive regulatory region and promoter is important for the stimulatory effect. The ability of these regulatory sequences to function and to determine cell-specific transcription does not appear to be an intrinsic property but also depends upon the context.