Multiple sclerosis (MS) is an inflammatory disease of the central nervous system that is thought to be a consequence of a microbial infection occurring in a genetically susceptible host in the mid-teenage years, leading to an autoimmune process that is manifested by clinical disease some years later. MS patients tend to be immune hyper-responders to a variety of microbial and self antigens, suggesting an element of immune dysregulation in the disease. Little is known about the mechanisms that lead to this pathological inflammatory response. Differential display was used to screen peripheral blood mononuclear cells (PBMC) from identical twins who are discordant for MS. One of the mRNAs detected from the normal twin but not from the MS twin codes for the bifunctional transcription factor Sp3. Although Sp3 was initially described as a dominant suppressor of gene transcription, it now appears to be a bifunctional molecule whose various isoforms may serve as either suppressor or activators of transcription. Genes whose transcription has been shown to be repressed by Sp3 include c-myc, HIV-1 LTR, dihydrofolate reductase, and elastin, while Sp3 activates TGF-beta, cyclin-dependent kinase inhibitor p21, and pyruvate kinase M genes. Using RT-PCR, Sp3 cDNA was amplified from 83% of control subjects, including those with rheumatoid arthritis and lupus, but was detected in only 21% of MS patients (p<0.001). The lack of Sp3 mRNA could not be explained on the basis of abnormally rapid degradation. We propose that transcription of the Sp3 gene is blocked in immune cells from most MS patients and that this leads to altered expression of one or more gene products involved in the development of CNS inflammation in the disease. The principal investigator hypothesizes that MS immune cells harbor one or more factors, possibly of microbial origin, that bind to the regulatory elements of the Sp3 gene and block its transcription. The 5' flanking regions of the Sp3 gene will be sequenced from our recently isolated Sp3 genomic clone. Nuclear and cytoplasmic extracts from PBMC will be screened by gel shift assays and DNaseI footprint analysis for factors present in MS but not control cells, that bind to one or more regulatory elements of the Sp3 gene. These factors will be purified and initial identification will be carried out by N-terminal amino acid analysis. In addition, purified human herpesvirus-6 and cytomegalovirus polypeptides will be studied for their ability to bind to Sp3 regulatory elements. Subsequent studies will determine if these factors/peptides exhibit an inhibitory influence on Sp3 gene transcription.
| Grekova, Maria C; Salerno, Kilian; Mikkilineni, Radha et al. (2002) Sp3 expression in immune cells: a quantitative study. Lab Invest 82:1131-8 |
| Grekova, M C; Scherer, S W; Trabb, J et al. (2000) Localization of the human SP3 gene to chromosome 7p14-p15.2. The lack of expression in multiple sclerosis does not reflect abnormal gene organization. J Neuroimmunol 106:214-9 |
