Neuronal apoptotic death induced by nerve growth factor (NGF) deprivation is reported to be in part mediated through a pathway that includes Rac1 and Cdc42, mitogen-activated protein kinase kinases 4 and 7 (MKK4 and -7), c-Jun N-terminal kinases (JNKs), and c-Jun. However, additional components of the pathway remain to be defined. We show here that members of the mixed-lineage kinase (

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We have identified a serum-inducible gene, relB, which encodes a protein of 558 amino acids containing a region with high similarity to c-Rel and other members of the Rel family. Transcriptional activation analysis of GAL4-RelB fusion proteins in yeast cells reveals that RelB contains in its C-terminal 180 amino acids a transcriptional activation domain. The N-terminal part including the region of similarity with the Rel family shows no detectable transcriptional activity. RelB does not bind with high affinity to NF-KB sites, but heterodimers between RelB and p50-NF-KB do bind to different NF-KtB-binding sites with a similar affinity to that shown by p50-NF-KB homodimers. However, RelB/p50-NF-KB heterodimers, in contrast to p50-NF-KB homodimers, transactivate transcription of a promoter containing a KB-binding site.Growth factors and other mitogens are capable of rapidly inducing a complex set of more than 100 genes in quiescent fibroblasts (1,13,31,32,38). These genes, which have been named immediate-early or early response genes, are transcriptionally activated within minutes after addition of growth factor or mitogen independently of de novo protein synthesis. Among these genes are several encoding bona fide or putative transcription factors such as members of the fos and jun families, zinc finger proteins (for reviews, see references 8, 22, and 33), or others containing undefined motifs like the Rel domain found in the proto-oncogene c-rel product (11,12,20) and the transcription factor NF-KB (7,16,28,44,47,49,51).The proto-oncogene c-rel (60) is the cellular homolog of the v-rel oncogene (53), isolated from reticuloendotheliosis virus strain T, a turkey-derived acutely transforming retrovirus (56) causing lymphoid leukemia. The c-rellv-rel genes are part of a rapidly growing family of transcription factors. One member of this family is the dorsal gene of Drosophila melanogaster, which is involved in establishing the dorsalventral axis (54) and is able to bind to NF-KB-like DNA sequences (23, 57). The other members are the transcription factor p50-NF-KB (also known as KBF1) with its precursor pl05-NF-KB (7,16,28,44), p50B(p49)-NF-KB with its precursor p97-NF-KB (6a, 51), and p65-NF-KB (47, 49). p50 and p65 form a heterodimer that is able to bind to NF-KB-binding sites found in many enhancers and promoters such as in the immunoglobulin kappa genes, interleukin-2, interleukin-6, ,-interferon, and others (for a review, see reference 35).All the members of the Rel family share a highly conserved domain of approximately 300 amino acids termed the Rel domain, which is considered to function as a DNAbinding and protein dimerization region with properties yet to be defined in detail. Additionally, all the members of this family show a regulated movement from the cytoplasm to the nucleus (for reviews, see references 17 and 36). In particular for the NF-KB complex it is known that p65 is able * Corresponding author.to interact with an inhibitor, IKB, which keeps it in the cytoplasm. After activation of cells, IKB is i...

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Although the mechanism of neuronal death

The Rel‐NF‐kappa B family of transcription factors plays a crucial role in the regulation of genes involved in inflammatory and immune responses. We demonstrate that in vivo, in contrast to the other members of the family, RelB associates efficiently only with NF‐kappa B1 (p105‐p50) and NF‐kappa B2 (p100‐p52), but not with cRel or p65. The RelB‐p52 heterodimers display a much lower affinity for I kappa B alpha than RelB‐p50 heterodimers or p65 complexes. However, similarly to the other Rel‐NF‐kappa B complexes, RelB‐p52 can upregulate the synthesis of I kappa B alpha leading to the cytoplasmic trapping of dimers which have a higher affinity for the inhibitor. We suggest that a hierarchy of interactions between I kappa B alpha and the different Rel‐NF‐kappa B complexes governs their cellular distribution. This results in the presence of two distinct pools of NF‐kappa B activity which differ in their composition: one a constitutive nuclear and the other an inducible cytoplasmic activity.

Although the interleukin-1␤ converting enzyme (ICE)/CED-3 family of proteases has been implicated recently in neuronal cell death in vitro and in ovo, the role of specific genes belonging to this family in cell death in the nervous system remains unknown. To address this question, we examined the in vivo expression of one of these genes, Ice, after global forebrain ischemia in gerbils. Using RT-PCR and Western immunoblot techniques, we detected an increase in the mRNA and protein expression of ICE in hippocampus during a period of 4 d after ischemia. Chromatin condensation was observed in CA1 neurons within 2 d after ischemia. Internucleosomal DNA fragmentation and apoptotic bodies were observed between 3 and 4 d after ischemia, a period during which CA1 neuronal death is maximal. In nonischemic brains, ICE-like immunoreactivity was relatively low in CA1 pyramidal neurons but high in scattered hippocampal interneurons. After ischemia, ICE-like immunoreactivity was not altered in these neurons. ICE-like immunoreactivity, however, was observed in microglial cells in the regions adjacent to the CA1 layer as early as 2 d after ischemic insult. The increase in ICE-like immunoreactivity was robust at 4 d after ischemia, a period that correlates with the DNA fragmentation observed in hippocampal homogenates of ischemic brains. These results provide the first evidence for the localization and induction of ICE expression in vivo after ischemia and suggest an indirect role for ICE in ischemic damage through mediation of an inflammatory response.