We studied the regulation of the transcription factors c-jun, junB and junD after sciatic nerve transection. RNA blot analysis identified that c-jun mRNA was dramatically induced after sciatic nerve transection. Immunobloting experiments showed that protein extract from dorsal root ganglia ipsilateral to nerve cut contained higher levels of Jun protein than the contralateral control DRG. The increase in protein and c-jun mRNA was not restricted to an exclusive-sized population of neurons but rather both in situ hybridization studies and immunocytochemical analysis identified neurons of different sizes which showed the increase. The JunB mRNA and protein were also induced after transection (two-three fold by day 1). JunD mRNA and protein exhibited a high constitutive level of expression in control DRG which persisted after sciatic nerve transection. DNA mobility shift experiments demonstrated that Jun transcription factors bind to both the AP-1 and the CRE sites. The experiments identified a DNA-protein complex specific to the AP-1 binding site. This complex was increased in the ipsilateral as compared to contralateral DRG extracts. The amount of DNA-protein complex was reduced by antisera directed against the protein products of c-jun, junB and junD, but was not altered when treated with a Fos antibody. These data suggest that the Jun family of transcription factors may play an important role in neuronal injury and nerve regeneration. A second area of research characterized a novel cDNA, DA 11, whose expression is regulated after sciatic nerve transection. The cDNA DA 11 was discovered during the screening of a cDNA library made from RNA extracted from DRG three days after sciatic nerve crush. The DA 11 cDNA was sequenced and our analysis showed that: (a) DA 11 encodes a lipid binding protein; (b) DA 11 mRNA is induced in the dorsal root ganglia after sciatic nerve cut or crush; (c) The higher levels of DA 11 mRNA in the DRG as compared with other tissues suggest that the protein product may play an important role in DRG neurons; (d) the up-regulation of DA 11 mRNA in the DRG after sciatic nerve transection suggests that it may play an important role during neuronal injury and/or nerve regeneration.
