Early Growth Response Family Research Articles

Regulation of transcriptional activity of the murine CD40 ligand promoter in response to signals through TCR and the costimulatory molecules CD28 and CD2.

We have analyzed the murine CD40 ligand promoter with regard to stimulation of transcriptional activity in Jurkat T cells after signaling via the TCR and the costimulatory molecules CD28 and CD2. TCR engagement was necessary for the induction of transcriptional activity from the CD40 ligand promoter, and costimulation through either CD28 or CD2 further increased the activity. Analysis of promoter deletants showed that the DNA elements needed for transcriptional activity induced by costimulatory molecules were located within two regions containing previously identified transcription factor NFAT sites. Further studies of the proximal NFAT site showed that it was not dependent on AP-1 binding for transcriptional activity induced by costimulation through CD28. Instead, a region between the TATA box and the proximal NFAT site was shown to bind proteins of the early growth response family and to contribute to NFAT-mediated transcriptional activation.

Specific induction of early growth response gene 1 in the lateral nucleus of the amygdala following contextual fear conditioning in rats

Although the amygdala is known to be crucial for fear conditioning, little is known about the molecular and cellular mechanisms in the amygdala that are important for fear conditioning. One possible mechanism may be the activation of immediate-early genes, which function as regulatory factors of transcriptional processes. To investigate whether one of the major immediate-early gene families is involved in the learning and memory of fear, we examined the effects of fear conditioning on the expression of the four members of the early growth response (EGR) gene family, EGR-1, EGR-2, EGR-3, and EGR-4. Image analysis of in situ hybridization of messenger RNA of the four family members was performed in the amygdala, hippocampus, and neocortex 15, 30 and 60 min following one-trial contextual fear conditioning. Rats were either handled, placed within the testing context without receiving the footshock, and received a footshock immediately upon placement within the context, or received a footshock after a 3-min delay (delayed-shock). Of the four groups, only the delayed-shock group exhibited a fear response (freezing). EGR-1 messenger RNA expression in the dorsolateral part of the lateral amygdaloid nucleus was significantly greater in the delayed-shock group compared with the other groups 15 and 30 min following the conditioning. The increased expression of EGR-1 was specifically localized to the lateral nucleus of the amygdala; expression in the hippocampus and cortex was not increased by fear conditioning. In contrast, the expression of EGR-2, EGR-3, and EGR-4 messenger RNA was not increased in the amygdala, hippocampus or cortex following fear conditioning. In addition, following a retention test conducted 24 h after fear conditioning, no increases were found in the expression of EGR-1 messenger RNA expression in the amygdala, hippocampus or cortex. The results demonstrate that of the four genes of the EGR family of transcription-regulatory factors, only EGR-1 messenger RNA in the dorsolateral portion of the lateral nucleus of the amygdala was specifically increased with contextual fear conditioning. It is suggested that EGR-1 plays a functional role during learning, but not retrieval, of contextual fear within the lateral nucleus of the amygdala.

Two Human Gene Families Display Preferences for Different Nucleotides and Have Distinct Codon Usage Patterns

Analysis of base composition has proven important for functional gene analysis. By comparing base composition and codon usage between two specific human gene families we were able to show a highly conserved nucleotide distribution among the members of one gene family and a significant difference between the two families. The two groups selected for analysis were the human factor H gene family, which represents six secreted human plasma proteins with functions in immune defense, and a class of four human zinc finger proteins, termed early growth response (EGR) proteins, which represent DNA-binding transcription factors. The nucleotide distribution of each gene family is distinct: members of the factor H gene family represent AT-rich genes, displaying an overall AT nucleotide content of 62.8% and a particular preference for A nucleotides (33.9%). In contrast, the EGR genes are GC-rich (55.9%) and C nucleotides are used in 31.2%. This nucleotide difference affects codon usage among synonymous codons and is considered of biological significance, as it affects DNA stability. The codon preference is particularly high at codon position 3, where each family selects for codons which have the preferred nucleotide at this silent third position. At position 3, A nucleotides are preferred by factor H genes in 36.3% of the 2,503 codons analyzed, compared to 10% of the 1,876 codons analyzed for the EGR family. In contrast, C nucleotides are used by the EGR family in 48.1%, compared to 16% of the triplets used by the factor H gene family. This comparison of two human gene families shows that nucleotide distribution and codon usage is not uniform within the human organism and the described differences most likely represent selection constraints between the polymorphic factor H and highly conserved EGR genes.

O-032. The role of early growth response family of transcription factors in male fertility

O-032. The role of early growth response family of transcription factors in male fertility

Repression of the HSV-1 latency-associated transcript (LAT) promoter by the early growth response (EGR) proteins: involvement of a binding site immediately downstream of the TATA box.

During herpes simplex virus (HSV) latency, in neurons of the nervous system, a single family of viral transcripts (the Latency-Associated Transcripts or LATs) are synthesized. Within the LAT promoter region, we have identified a consensus sequence for the EGR proteins in an unusual position immediately downstream of the TATA box. The early growth response (EGR) proteins are rapidly induced in cells by stimuli which also induce HSV to reactivate from latency. In order to determine if EGR proteins play any role in control of LAT transcription, we have analyzed the interactions between EGR proteins and the LAT promoter. Gel retardation and DNase I protection assays demonstrated that EGR1 zinc finger protein bound specifically to the LAT promoter region EGR consensus sequence. To determine if EGR proteins could modulate transcription through the LAT promoter, cotransfection assays were performed using chloramphenicol acetyltransferase (CAT) reporter constructs driven by either the wild-type LAT promoter or a LAT promoter with a mutated EGR binding site. Contransfection of the wild-type LAT promoter construct with EGR expression plasmids resulted in inhibition of the basal level of CAT activity with EGR-2 but not EGR-1 or 3. However, normal levels of CAT activity were observed in cotransfections using the mutant LAT promoter CAT construct suggesting that repression was mediated by the binding of EGR-2 proteins to the LAT promoter. Furthermore, data from combination binding assays using EGR1 and TATA binding protein (TBP) in vitro support the hypothesis that binding of EGR proteins to the LAT promoter prevents binding of TBP and thus suppresses transcription. These results may provide a link between stress responses in neurons of the CNS which activate the EGR family of proteins and HSV reactivation from latency due to the same stress response.