CRTAM is negatively regulated by ZEB1 in T cells.

T cell activation leads to the induction of genes that are required for appropriate immune responses. This includes CRTAM (Class-I MHC-restricted T cell associated molecule), a protein that plays a key role in T cell development, proliferation, and generating cell polarity during activation. We previously characterized the CRTAM promoter and described how AP-1 family members are important for inducing CRTAM expression upon antigenic activation. Here, we show that CRTAM is a molecular target for ZEB1 (zinc finger E-box-binding protein), a homeodomain/Zn finger transcription factor. Overexpression of ZEB1 repressed CRTAM promoter activity, as well as endogenous CRTAM levels in human T cells. ZEB1-mediated transcriptional repression was abolished when E-box-like elements in the CRTAM promoter are mutated. In summary, ZEB1 functions as a transcriptional repressor for the CRTAM gene in both non-stimulated and stimulated T cells, thereby modulating adaptive immune responses.

Transcriptional analysis of the EhPgp1 promoter of Entamoeba histolytica multidrug-resistant mutant.

We present here the cloning and characterization of the EhPgp1 multidrug resistance gene promoter isolated from the Entamoeba histolytica drug-resistant mutant clone C2. The EhPgp1 promoter lacks the typical TATA box and the transcriptional initiation sequences described for other E. histolytica promoters. The major transcription initiation site of the EhPgp1 gene was located at the ATG start codon. The EhPgp1 core promoter located within the first 244 base pairs showed a higher chloramphenicol acetyltransferase expression in the transfected trophozoites of clone C2 than in those of the sensitive clone A. Gel shift assays revealed three specific DNA-protein complexes (Ia, IIa, and IIIc) using nuclear extracts from clone C2, whereas three main complexes (If, IIf, and IIg) were limited to clone A. Competition assays suggested the presence of C/EBP-like and OCT-like proteins in complexes Ia and IIa, respectively, probably involved in the expression of the EhPgp1 gene, whereas complex IIIc was competed by GATA-1, C/EBP, OCT, and HOX oligonucleotides. Thus, differential DNA-protein complexes may be formed by transcriptional factors involved in the regulation of the EhPgp1 gene expression.

Transcriptional analysis of the 5'-noncoding region of the human involucrin gene.

Human involucrin whose gene transcription is directed by a 2456-nucleotide (nt) 5'-noncoding region is a structural component of the epithelial cornified layer. Transient transfection assays demonstrated that this region is transcriptionally active in multiplying keratinocytes and is enhanced by 2 mM CaCl2 treatment. Calcium-independent transcriptional activity and the interaction with the AP-1 transcriptional factor was located on the proximal part (nt -159 to -1) of the 5'-noncoding region. However, CaCl2 responsiveness was mapped to a distal 1185-nt fragment (nt -2456 to -1272). Moreover, this fragment potentiated the Herpes simplex thymidine kinase promoter in normal keratinocytes and is responsive to calcium treatment in a cell type-specific manner. Interestingly, the absence of a 491-nt fragment located between the two enhancer domains (nt -651 to -160) resulted in transcriptional activation in multiplying keratinocytes. This fragment interacts with AP-1 and the YY1 transcriptional silencer. It is concluded that human involucrin 5'-noncoding region contains at least three regulatory domains, a distal CaCl2-responsive enhancer, a putative transcriptional silencer (that interacts with AP-1 and YY1), and a proximal enhancer/promoter (that interacts with AP-1). Thus, this study demonstrates the presence of particular transcriptional factors can potentially regulate the human involucrin expression.

[Genetic regulation of human genital papillomaviruses]. / Regulación genética de los papilomavirus humanos genitales.

Human papillomavirus (HPV) specifically infect stratified epithelial cells, causing benign and malignant neoplasia. Several elements directing this virus' genetic expression are present in a non-coding region called LCR. HPV infection starts in the basal cells of stratified epithelia, where a particular combination of cellular factors interacting with the LCR starts the transcription of the viral E6 and E7 oncogenes. The E6 and E7 genes alter the cell cycle because they interact and inactivate tumor suppressor proteins: E6 binds and degrades protein p53 and E7 associates with p105RB. E1 and E2 are the next synthesized proteins. E2 blocks the early transcription and permits E1 specific binding to the viral origin of replication located within the LCR, initiating the viral genome replication. Following the course of viral infection, the E2-induced E6 and E7 down-regulation releases p53 and p105RB proteins, and the differentiation process can continue. Then, a putative late promoter can activate the capsid genes L1 and L2. At this step, mature virions can be detected in the upper layers of the epithelium. Disruption in E2 gene transcription is usually associated to genital malignant neoplasia. In the absence of E2, E6 and E7 remain constitutively expressed, sustaining the immortality of the infected cell and blocking the epithelial differentiation program.